Small runner, sometimes in form, gets cut (5)
I believe the answer is:
share
'cut' is the definition.
(I've seen this before)
'small runner' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'runner' becomes 'hare' (fast-running animal).
's'+'hare'='SHARE'
'sometimes in form gets' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for share that I've seen before include "Portion, maybe of capital" , "Division" , "Give portion to others" , "hand pieces out" , "Allotted portion" .)