Fifty in plant spend money extravagantly (7)
I believe the answer is:
splurge
'spend money extravagantly' is the definition.
I can't judge whether this defines the answer.
'fifty in plant' is the wordplay.
'fifty' becomes 'l' (Roman numeral).
'in' means one lot of letters goes inside another.
'plant' becomes 'spurge' (spurge is a shrub).
'l' going into 'spurge' is 'SPLURGE'.
Can you help me to learn more?
(Other definitions for splurge that I've seen before include "Spend money freely, be extravagant" , "Spend lavishly" , "Lash out" , "Fork out" , "Squander" .)