Chap with a red back, usually mounted (6)
I believe the answer is:
ladder
'chap with a red back usually mounted' is the definition.
I can't judge whether this defines the answer.
'chap with a red back' is the wordplay.
'chap' becomes 'lad' ().
'with' is a charade indicator (letters next to each other).
'back' is a reversal indicator.
'red' backwards is 'der'.
'lad'+'der'='LADDER'
Can you help me to learn more?
(Other definitions for ladder that I've seen before include "1 [UNLUCKY FOR SOME]" , "Vertical run in tights" , "Framework for scaling, usually portable" , "Companionway" , "Scaling device" .)