Generate designs for an adolescent (8)
I believe the answer is:
teenager
'for an adolescent' is the definition.
(synonyms)
'generate designs' is the wordplay.
'designs' indicates anagramming the letters (I've seen 'design' mean this).
'generate' anagrammed gives 'TEENAGER'.
(Other definitions for teenager that I've seen before include "Old child or young adult?" , "one with an unpredictable nature" , "Generate (anag)" , "hormonal problem?" , "Young person" .)