Holiday? Get flowery garland, certainly (7)
I believe the answer is:
leisure
'holiday?' is the definition.
(holiday is a kind of leisure)
'get flowery garland certainly' is the wordplay.
'get' means one lot of letters go next to another.
'flowery garland' becomes 'lei'.
'certainly' becomes 'sure' ('sure' can be a synonym of 'certainly').
'lei' next to 'sure' is 'LEISURE'.
(Other definitions for leisure that I've seen before include "idle hours" , "Free time, comfort and convenience" , "Freedom from work" , "Time for relaxing" , "Breathing space" .)