On the border, worker measures birds (5)

I believe the answer is:

wrens

'birds' is the definition.
(wren is a kind of bird)

'on the border worker measures' is the wordplay.
'on' says to put letters next to each other.
'the border' says to hollow out the word (remove centre letters) (I've seen 'borders' mean this).
'measures' becomes 'ens' (en is a kind of measure).
'worker' with its centre taken out is 'wr'.
'wr' next to 'ens' is 'WRENS'.

(Another definition for wrens that I've seen is " Small brown birds".)

I've seen this clue in the Sydney Morning Herald.

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