Start with yen lad's saved (6,2)
I believe the answer is:
switch on
'start' is the definition.
(I've seen this before)
'with yen lad's saved' is the wordplay.
'with' becomes 'w' (abbreviation).
'yen' becomes 'itch' (I've seen this before).
'lad' becomes 'son' (lad can informally mean a young boy).
'saved' means one lot of letters goes inside another (save can mean to keep hold of).
'w'+'itch'='witch'
'witch' put within 'son' is 'SWITCH ON'.
(Other definitions for switch on that I've seen before include "Give power" , "fire" , "Operate" , "get to work" , "Make contact with" .)