Trouble with lapse showing up a handsome young man (6)
I believe the answer is:
adonis
'a handsome young man' is the definition.
(I've seen this before)
'trouble with lapse showing up' is the wordplay.
'trouble' becomes 'ado' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'lapse' becomes 'sin' (I've seen this in other clues).
'showing up' is a reversal indicator.
'sin' written backwards gives 'nis'.
'ado'+'nis'='ADONIS'
(Other definitions for adonis that I've seen before include "Extremely attractive young man from Greek mythology" , "male looker" , "Greek idol" , "lovely man" , "striking youth" .)