One who's likely to ridicule small chest (7)
I believe the answer is:
scoffer
'one who's likely to ridicule' is the definition.
I can't tell whether this definition defines the answer.
'small chest' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'chest' becomes 'coffer' (coffer is a kind of chest).
's'+'coffer'='SCOFFER'
Can you help me to learn more?
(Other definitions for scoffer that I've seen before include "One who pokes fun" , "pig" , "he eats very quickly" , "diner" , "Hungry type" .)