Unlikely way of learning about return of the setter (6)
I believe the answer is:
remote
'unlikely' is the definition.
(I've seen this before)
'way of learning about return of the setter' is the wordplay.
'way of learning' becomes 'rote' (I've seen this before).
'about' means one lot of letters goes inside another.
'return of' is a reversal indicator.
'the setter' becomes 'me' (the setter of the clue).
'me' backwards is 'em'.
'rote' placed around 'em' is 'REMOTE'.
(Other definitions for remote that I've seen before include "Far way like meteor" , "Far-flung" , "Cold" , "Distant, far away" , "At a great distance" .)