Teenager goes off to evolve (8)
I believe the answer is:
generate
'evolve' is the definition.
(I've seen this before)
'teenager goes off' is the wordplay.
'goes off' is an anagram indicator.
'teenager' is an anagram of 'GENERATE'.
'to' acts as a link.
(Other definitions for generate that I've seen before include "evolve" , "Create for teenager" , "Produce, electricity say" , "Beget" , "Give rise to" .)