Garland is certain to have some spare time (7)
I believe the answer is:
leisure
'some spare time' is the definition.
(I've seen this in another clue)
'garland is certain' is the wordplay.
'garland' becomes 'lei' (a lei is a garland of flowers).
'is certain' becomes 'sure' (synonyms).
'lei'+'sure'='LEISURE'
'to have' is the link.
(Other definitions for leisure that I've seen before include "Recreation time" , "casual wear" , "Use lire (anag)" , "Non-work activity" , "idle hours" .)