Exhausted writer added to stanza (5)
I believe the answer is:
spent
'exhausted' is the definition.
(I know that exhausted can be written as spent)
'writer added to stanza' is the wordplay.
I cannot quite see how this works, but
'writer' could be 'pen' (something which writes) and 'pen' is located in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for spent that I've seen before include "Worn out, having laid out money" , "Worn Out, exhausted" , "Drained of energy - or paid out" , "Worn out - after shopping?" , "Exhausted, having paid money?" .)