Type of coffee — rep's working fuel? (8)
I believe the answer is:
espresso
'type of coffee' is the definition.
(I've seen this in another clue)
'rep's working fuel?' is the wordplay.
'working' is an anagram indicator.
'fuel?' becomes 'Esso' (Esso is a fuel company).
'reps' with letters rearranged gives 'espr'.
'espr'+'esso'='ESPRESSO'
(Other definitions for espresso that I've seen before include "Barista's beverage" , "Italian-style coffee" , "It's made by forcing steam through ground coffee beans" , "Coffee (S, not X)" , "This may keep someone awake!" .)