A small amount of money for a sea creature (5)
I believe the answer is:
squid
'sea creature' is the definition.
(squids live in the sea)
'a small amount of money' is the wordplay.
I cannot really understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is present in the answer.
'amount' could be 'quid' (quid is a kind of amount) and 'quid' is found in the answer.
No letters remain.
This explanation may well be incorrect...
'for a' acts as a link.
Can you help me to learn more?
(Other definitions for squid that I've seen before include "Marine cephalopod" , "Tentacled marine creature" , "Eight-armed creature" , "Edible eight-arm mollusc" , "Ten-armed mollusc" .)