Supply, eg oil? No, USA is rich in oil (10)
I believe the answer is:
oleaginous
'rich in oil' is the definition.
'supply eg oil? no usa' is the wordplay.
'supply' indicates an anagram ('supply' is an adverb here, so in a 'supple' way).
'eg'+'oil'+'no'+'usa'='egoilnousa'
'egoilnousa' with letters rearranged gives 'OLEAGINOUS'.
'is' acts as a link.
(Other definitions for oleaginous that I've seen before include "oily" , "fawning" .)