Fascinated in period before spring (10)
I believe the answer is:
spellbound
'fascinated' is the definition.
(I know that fascinated can be written as spellbound)
'period before spring' is the wordplay.
'period' becomes 'spell' (spell can mean a period of time).
'before' says to put letters next to each other.
'spring' becomes 'bound' (synonyms).
'spell'+'bound'='SPELLBOUND'
'in' acts as a link.
(Other definitions for spellbound that I've seen before include "Captivated" , "Transfixed, mesmerised" , "Bewitched" , "enthralled" , "frozen" .)