Bound to have instant cut in relaxation (8)
I believe the answer is:
restrict
'bound' is the definition.
(I know that bound can be written as restrict)
'instant cut in relaxation' is the wordplay.
'instant' becomes 'trice' (both can mean a short amount of time).
'cut' means to remove the last letter.
'in' means one lot of letters goes inside another.
'relaxation' becomes 'rest' (synonyms).
'trice' with its final letter taken off is 'tric'.
'tric' placed inside 'rest' is 'RESTRICT'.
'to have' is the link.
(Other definitions for restrict that I've seen before include "Keep within bounds" , "Deprive of freedom" , "Limit, inhibit" , "Place limit on" , "'Restrain, limit (8)'" .)