Handy American fuel supply (6)
I believe the answer is:
useful
'handy' is the definition.
(thesaurus)
'american fuel supply' is the wordplay.
'american' becomes 'us'.
'supply' is an anagram indicator (supply of letters to make).
'fuel' anagrammed gives 'eful'.
'us'+'eful'='USEFUL'
(Other definitions for useful that I've seen before include "Suitable for practical purpose" , "Advantageous, serviceable" , "Expedient" , "Of service" , "Functional, handy" .)