Recycling old answers

Question

Each of the puzzles below gives a two-word answer. Solve the puzzles and arrange the resulting 16 words into four groups of four, each with a common theme. The resulting group names form a clue for the final answer.

1. Written every which way
2. A manager's dilemma
3. Keeping you safe
4. Coordinated efforts
5. Contours of a clandestine nature
6. Between two walls
7. Pulling a fast one
8. In excess I'm lethal

Answer 1

The four groups are:

1

London: Fire, Marathon, Olympics, Underground

2

Tower: Cell, Devils, Ivory, Water

3

Guard: Coast, National, Old, Security - thanks @arbitrahj for this one

4

Duty: Cycle, Double, Heavy, Line

The answers spell out

London Tower Guard Duty, which seems to be hinting at the Yeomen Warders, whose duty it is to guard the Tower of London.

Answer 2

Aggregated Answers from the Puzzles:

1. Written every which way

   Ivory Coast

2. A manager's dilemma

   Fire Devils

3. Keeping you safe

   National Security

4. Coordinated efforts -

   Old Olympics

5. Contours of a clandestine nature

   Underground Line

6. Between two walls

   Cell Cycle

7. Pulling a fast one

   Double Marathon

8. In excess I'm lethal

   Heavy Water

Answer 3

Some initial guesses:

1.

Life Line, Cycle, Double, Cell.

2.

Guard Old, National, Security, Coast

3.

Medal(metal) Heavy, Devils, underground, olympics

4. ??? Kinda falls apart

red white and blue?? Fire Water, Ivory, marathon

Or

rings fire, olympics, underground, cell

Which moves

Water to life

Leaving

Heavy, devils, ivory, marathon which is still ?????

Answer 4

Possible Groupings [1,2,3,4 contradict with each other, just listing some possible combinations]

1:

Lines/Contours: Coast, Line, Marathon, ?

2:

Sports [unlikely]: Olympics, Marathon, ?, ?

3:

Metal: Devils (devils metal: silver), Heavy (heavy metal), Underground?, ?

4:

Loops: Cycle, Olympics (5 cicles on flag), Underground (System map looks like a loop), ?