Spend a penny gathering mud ants (8)

I believe the answer is:

pismires

'ants' is the definition.
('pismire' can be a synonym of 'ant')

'spend a penny gathering mud' is the wordplay.
'spend a penny' becomes 'piss' (synonyms).
'gathering' indicates putting letters inside.
'mud' becomes 'mire' (synonyms).
'piss' enclosing 'mire' is 'PISMIRES'.

I've seen this clue in The Guardian.

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