Ape moving like that finished in thick fog (3,4)
I believe the answer is:
pea soup
'fog' is the definition.
(I know that pea soup is a type of fog)
'ape moving like that finished in thick' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'ape' is 'pea' which is within the answer.
'finished' could be 'up' (eg 'time's up' means the time is finished) and 'up' is found in the answer.
'like that' could be 'so' (as in 'like so') and 'so' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pea soup that I've seen before include "Dish like old London fog" , "very hazy situation" , "Hot dish (like a fog?)" , "starter course?" , "Food - thick yellow fog" .)