Games a police chief overheard in thick fog (3-6)
I believe the answer is:
pea-souper
'thick fog' is the definition.
(I've seen this before)
'games a police chief overheard in' is the wordplay.
'games' becomes 'PE' (Physical Education, also called games).
'police' becomes 'super' (I can't explain this - if you can you should give a lot more credence to this answer).
'chief' says to take the initial letters.
'in' means one lot of letters goes inside another.
The first letter of 'overheard' is 'o'.
'super' placed around 'o' is 'souper'.
'pe'+'a'+'souper'='PEA-SOUPER'
Can you help me to learn more?
(Other definitions for pea-souper that I've seen before include "Thick, dirty, yellowish fog" , "Dense, dirty fog" , "Thick smokey fog" , "Dense yellow fog" .)