Youngster gets a lot of money for instrument (4,5)
I believe the answer is:
baby grand
'instrument' is the definition.
(baby grand is a kind of instrument)
'youngster gets a lot of money' is the wordplay.
'youngster' becomes 'baby' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'gets' means one lot of letters go next to another.
'a lot of money' becomes 'grand'.
'baby'+'grand'='BABY GRAND'
'for' is the link.
Can you help me to learn more?
(Other definitions for baby grand that I've seen before include "Infant piano?" , "Smaller piano" , "message of proud new parents?" , "Type of piano" , "Instrument" .)