Backtracking, Sir Keir occasionally delivers step change? (5)
I believe the answer is:
riser
'step change?' is the definition.
'riser' can be an answer for 'step' (I've seen this in another clue). I'm unsure of the 'change?' bit.
'backtracking sir keir occasionally' is the wordplay.
'backtracking' shows that the letters should be reversed in order.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
The alternating letters of 'keir' are 'er'.
'sir' back-to-front is 'ris'.
'ris'+'er'='RISER'
'delivers' acts as a link.
Can you help me to learn more?
(Other definitions for riser that I've seen before include "Vertical piece between two steps of stairs" , "One who has stopped sleeping" , "Part of flight" , "Vertical piece between two stair treads" , "He gets up" .)