Create when gate crashing Rene comes in (8)
I believe the answer is:
generate
'create' is the definition.
(generating is a kind of creating)
'gate crashing rene comes in' is the wordplay.
'crashing' is an anagram indicator.
'comes in' is an insertion indicator.
'rene' anagrammed gives 'ener'.
'gate' placed around 'ener' is 'GENERATE'.
'when' is the link.
(Other definitions for generate that I've seen before include "available in form" , "Give rise to" , "Engender" , "Cause to arise; produce" , "Produce, electricity say" .)