Period certain to get us enthralled (10)
I believe the answer is:
spellbound
'enthralled' is the definition.
(thesaurus)
'period certain' is the wordplay.
'period' becomes 'spell' (spell is a kind of period**).
'certain' becomes 'bound' (as in the phrase 'it's bound to be').
'spell'+'bound'='SPELLBOUND'
'to get us' acts as a link.
(Other definitions for spellbound that I've seen before include "Bewitched" , "Transfixed, mesmerised" , "Fascinated" , "Held rapt" , "Entranced" .)