Challenging nurses over secret supply (5)
I believe the answer is:
hoard
'secret supply' is the definition.
'hoard' can be an answer for 'supply' (I've seen this before). I'm not certain of the 'secret' bit.
'challenging nurses over' is the wordplay.
'challenging' becomes 'hard' (similar in meaning).
'nurses' means one lot of letters goes inside another (nurse can mean to hold onto or harbour).
'over' becomes 'o' (cricket abbreviation).
'hard' going around 'o' is 'HOARD'.
Can you help me to learn more?
(Other definitions for hoard that I've seen before include "One's savings" , "Collection" , "Amass and store privately" , "A lot of people" , "Accumulated store" .)