Periods in which wandering ant makes no progress (9)

I believe the answer is:

stagnates

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Here is my best explanation:

'makes no progress' is the definition.

'periods in which wandering ant' is the wordplay.
'periods' becomes 'stages' (e.g. many stages of development**).
'in which' is an insertion indicator.
'wandering' indicates an anagram.
'ant' with letters rearranged gives 'nat'.
'stages' going around 'nat' is 'STAGNATES'.

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This clue was last seen in The Times

(Other definitions for stagnates that I've seen before include "Festers", "doesn't develop" and "becomes inactive".)

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