Spare former lover found on Irish beach (5)

I believe the answer is:

extra

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'spare' is the definition.
(synonyms)

'former lover found on irish beach' is the wordplay.
'former lover' becomes 'ex' (ex-lover).
'found on irish beach' becomes 'tra' (I can't explain this - if you can you should give a lot more credence to this answer).
'ex'+'tra'='EXTRA'

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(Other definitions for extra that I've seen before include "Accessory" , "Cricket run; unusually" , "Possibly overthrow" , "Wide, no-ball, leg bye, etc" , "someone in a crowd scene" .)

I've seen this clue in The Irish Times.

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