Man's riding garb (5)
I believe the answer is:
chaps
'man's riding garb' is the definition.
I can't tell whether this definition defines the answer.
'man's riding garb' is the wordplay.
'man' becomes 'chap' (I've seen this in other clues).
'riding garb' becomes 's' (I can't explain this - if you can you should believe this answer much more).
'chap'+'s'='CHAPS'
Can you help me to learn more?
(Other definitions for chaps that I've seen before include "providing leather bags from US" , "Cowboy's trousers; men" , "Guy's" , "Men; leather trousers" , "Cowboy leggings" .)