Disgusting gangster swallowed by sea creature (7)
I believe the answer is:
squalid
'disgusting' is the definition.
(thesaurus)
'gangster swallowed by sea creature' is the wordplay.
'gangster' becomes 'al' (Al Capone).
'swallowed by' is an insertion indicator.
'sea creature' becomes 'squid' (I've seen this before**).
'al' put into 'squid' is 'SQUALID'.
(Other definitions for squalid that I've seen before include "run down" , "Dirty and neglected" , "Dirty, unpleasant" , "Wretched, filthy" , "Morally repulsive" .)