Annoyance with former partner replacing account during holiday (8)
I believe the answer is:
vexation
'annoyance' is the definition.
(synonyms)
'former partner replacing account during holiday' is the wordplay.
I cannot quite understand how this works, but
'former' could be 'ex' and 'ex' is present in the answer.
'partner' could be 'n' and 'n' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'with' acts as a link.
(Other definitions for vexation that I've seen before include "Nuisance, aggravation" , "State of being annoyed or worried" , "Worry, annoyance" , "Chagrin" .)