Suffers since one's confined by nurse turning up (8)
I believe the answer is:
agonises
'suffers' is the definition.
(agonising is a kind of suffering)
'since one's confined by nurse turning up' is the wordplay.
'since' becomes 'ago' (I've seen this before).
'one's' becomes 'is' (Roman numeral).
'confined by' indicates putting letters inside.
'nurse' becomes 'sen' (I've seen this before**).
'turning up' is a reversal indicator.
'sen' reversed gives 'nes'.
'is' going within 'nes' is 'nises'.
'ago'+'nises'='AGONISES'
(Other definitions for agonises that I've seen before include "Worries intensely" , "struggles" , "Suffers mental pain or worries" .)