Take vital supply yielding plenty of gas (9)
I believe the answer is:
talkative
'yielding plenty of gas' is the definition.
'take vital supply' is the wordplay.
'supply' is an anagram indicator (supply of letters to make).
'take'+'vital'='takevital'
'takevital' is an anagram of 'TALKATIVE'.
(Other definitions for talkative that I've seen before include "Chatty" , "Wordy" , "Garrulous, loquacious" , "Voluble" , "Inclined to speak" .)