Suggest nothing small found in crater (5)
I believe the answer is:
posit
'suggest' is the definition.
(I know that posit is a type of suggest)
'nothing small found in crater' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'small' becomes 's' (abbreviation - e.g. clothes size).
'found in' means one lot of letters goes inside another.
'crater' becomes 'pit' (I've seen this in another clue).
'o'+'s'='os'
'os' going within 'pit' is 'POSIT'.
(Other definitions for posit that I've seen before include "Put forward (argument)" , "Put forward (as fact)" , "forward-looking statement" , "Put forward (something) as a given" , "Put forward as basis for discussion" .)