Four gestatory implants have eggs on (5)

I believe the answer is:

urges

'eggs on' is the definition.
(I've seen this before)

'four gestatory implants have' is the wordplay.
'have' says the answer is hidden in the clue.
'URGES' is hidden within 'four gestatory implants'.

(Other definitions for urges that I've seen before include "Persuades to do something" , "Drives" , "Advocates strongly" , "Strong impulses" , "Encourages" .)

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

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