Sat back outside. Rep returned with slender candles (6)
I believe the answer is:
tapers
'slender candles' is the definition.
(I've seen this in another clue)
'sat back outside rep returned' is the wordplay.
'back' says the letters should be written in reverse.
'outside' means one lot of letters goes inside another.
'returned' says the letters should be written in reverse.
'sat' written backwards gives 'tas'.
'rep' backwards is 'per'.
'tas' enclosing 'per' is 'TAPERS'.
'with' acts as a link.
(Other definitions for tapers that I've seen before include "Diminishes gradually" , "Prates about candle lighters" , "Long thin candles" , "Repast with slender candles" , "Prates about slender candles" .)