Without fuel supply? It's terrible (6)
I believe the answer is:
woeful
'terrible' is the definition.
(thesaurus)
'without fuel supply?' is the wordplay.
'without' becomes 'wo' (abbreviation of 'without', normally with a slash).
'supply?' is an anagram indicator (in a supple way).
'fuel' with letters rearranged gives 'eful'.
'wo'+'eful'='WOEFUL'
'it's' is the link.
(Other definitions for woeful that I've seen before include "Miserable" , "Pathetic" , "Pitiable" , "'Wilful waste makes ...... want'" , "We foul, being sad and deplorable" .)