Necessary end: fuel exploding (7)
I believe the answer is:
needful
'necessary' is the definition.
(similar in meaning)
'end fuel exploding' is the wordplay.
'exploding' indicates anagramming the letters.
'end'+'fuel'='endfuel'
'endfuel' anagrammed gives 'NEEDFUL'.
(Other definitions for needful that I've seen before include "Poverty-stricken" , "Nude elf (anag.)" , "poor" , "Required" , "Indispensable" .)