Knight on board runs in leggings (5)
I believe the answer is:
horse
'knight on board' is the definition.
'horse' can be an answer for 'knight' (synonyms). I am unsure of the 'on board' bit.
'runs in leggings' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'in' is an insertion indicator.
'leggings' becomes 'hose' (I've seen this in another clue).
'r' going within 'hose' is 'HORSE'.
Can you help me to learn more?
(Other definitions for horse that I've seen before include "See 13" , "Equine animal" , "Equine quadruped" , "charger?" , "gym apparatus" .)