Loose net and fish intertwine (8)
I believe the answer is:
entangle
'intertwine' is the definition.
(thesaurus)
'loose net and fish' is the wordplay.
'loose' indicates an anagram (letters are loosened from their original positions).
'and' means one lot of letters go next to another.
'fish' becomes 'angle' (angling is a kind of fishing).
'net' anagrammed gives 'ent'.
'ent'+'angle'='ENTANGLE'
(Other definitions for entangle that I've seen before include "Ravel" , "catch" , "Ensnare" , "Involve in complications" , "Entwine or involve in something complicated" .)