Bunch of notes one found in gully (4)
I believe the answer is:
'gully' is the definition.
(I know that wadi is a type of gully)
'bunch of notes one' is the wordplay.
'bunch of notes' becomes 'wad' (wad of banknotes).
'one' becomes 'i' (Roman numeral).
'found in' is the link.
(Other definitions for wadi that I've seen before include "Seasonal water channel" , "Seasonally wet ravine" , "Mainly dry ravine" , "Seasonal water course (in Arabic-speaking lands)" , "(Usually) dry desert riverbed" .)