Criminal is more violent around summer time (7)
I believe the answer is:
mobster
'criminal' is the definition.
(I know that mobster is a type of criminal)
'more violent around summer time' is the wordplay.
'violent' is an anagram indicator (I've seen this in other clues).
'around' indicates putting letters inside.
'summer time' becomes 'bst' (British Summer Time).
'more' anagrammed gives 'moer'.
'moer' placed around 'bst' is 'MOBSTER'.
'is' is the link.
(Other definitions for mobster that I've seen before include "family man" , "Criminal gang member" , "Hoodlum" , "Gangster" , "Mafioso" .)