Special fuel, I hesitate to say, that’s given away too much (7)
I believe the answer is:
spoiler
'that's given away too much' is the definition.
(a spoiler gives away details of a story)
'special fuel i hesitate to say' is the wordplay.
'special' becomes 'sp'.
'fuel' becomes 'oil' (I've seen this before).
'i hesitate to say' becomes 'er' (expression used when hesitating).
'sp'+'oil'+'er'='SPOILER'
(Other definitions for spoiler that I've seen before include "Disruptive competitor" , "Aerofoil at the back of a car to reduce lift at high speeds" , "Device increasing drag" , "Device which improves car's roadholding at speed" , "attachment to racing car" .)