Periods in which wandering ant makes no progress (9)

I believe the answer is:
stagnates
Here is my best explanation:
'makes no progress' is the definition.
'periods in which wandering ant' is the subsidiary indication.
'periods' becomes 'stages' (e.g. many stages of development**).
'in which' indicates putting letters inside.
'wandering' indicates an anagram.
'ant' anagrammed gives 'nat'.
'stages' enclosing 'nat' is 'stagnates'.
This clue was last seen in The Times
(Another definition for stagnates that I've seen is "Festers".)

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