Play, or shelter on course (6)
I believe the answer is:
leeway
'play' is the definition.
(I've seen this before)
'shelter on course' is the wordplay.
'shelter' becomes 'lee' (as in lee side, the side sheltered from wind).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'course' becomes 'way' (way is a kind of course).
'lee'+'way'='LEEWAY'
'or' acts as a link.
(Other definitions for leeway that I've seen before include "Allowance" , "Amount of freedom" , "Give" , "Drift to make up" , "Scope for freedom of movement or action" .)