Back favourite to accept current special treatment? (3,6)
I believe the answer is:
'special treatment?' is the definition.
(I've seen this before)
'back favourite to accept current' is the wordplay.
'back' becomes 'rear' (similar in meaning).
'favourite' becomes 'pet' (synonyms).
'to accept' means one lot of letters goes inside another.
'current' becomes 'dc'.
'rearpet' placed around 'dc' is 'RED CARPET'.
(Other definitions for red carpet that I've seen before include "sort of deferential treatment?" , "for star treatment" , "see VIP on this?" , "sort of treatment for special visitors?" , "Welcoming walkway" .)