Give in, hiding large disappointment (4)
I believe the answer is:
blow
'disappointment' is the definition.
(blow can mean a setback or difficulty)
'give in hiding large' is the wordplay.
'give in' becomes 'bow' (synonyms).
'hiding' means one lot of letters goes inside another.
'large' becomes 'L' (eg in clothes sizes).
'bow' enclosing 'l' is 'BLOW'.
(Other definitions for blow that I've seen before include "Blast" , "Use pipe for" , "'..., ..., thou winter wind' (As You Like It)" , "force through pipe" , "Clip" .)