Nasty gremlin runs out to fraternise (6)
I believe the answer is:
mingle
'fraternise' is the definition.
(thesaurus)
'nasty gremlin runs out' is the wordplay.
'nasty' indicates anagramming the letters (a nasty or wrong spelling).
'runs' becomes 'r' (cricket abbreviation).
'out' is a deletion indicator.
'gremlin' with 'r' removed is 'gemlin'.
'gemlin' anagrammed gives 'MINGLE'.
'to' is the link.
(Other definitions for mingle that I've seen before include "Circulate at a party" , "Mix (socially)" , "Mix - associate" , "Dawn song, poem" , "Mix among others" .)