Relating to currency note army supply (8)
I believe the answer is:
monetary
'relating to currency' is the definition.
(I've seen this before)
'note army supply' is the wordplay.
'supply' indicates an anagram (in a supple way).
'note'+'army'='notearmy'
'notearmy' anagrammed gives 'MONETARY'.
(Other definitions for monetary that I've seen before include "involving finances" , "of bread" , "Army note (anag) - financial" , "Fiscal" , "Relating to currency" .)