Nut caught fish in trench (8)
I believe the answer is:
encroach
'trench' is the definition.
(thesaurus)
'nut caught fish' is the wordplay.
'nut' becomes 'en' ('nut' is printers' slang for an en space).
'caught' becomes 'c' (cricket abbreviation).
'fish' becomes 'roach' (roach is a kind of fish**).
'en'+'c'+'roach'='ENCROACH'
'in' acts as a link.
(Other definitions for encroach that I've seen before include "Gradually intrude (on person's area)" , "Intrude on another's property or rights" , "Impinge, infringe" , "Intrude on someone's territory or time" , "Go past a normal limit" .)