Start siege, developing plans (10)

I believe the answer is:

strategies

'plans' is the definition.
(strategy is a kind of plan)

'start siege developing' is the wordplay.
'developing' indicates an anagram.
'start'+'siege'='startsiege'
'startsiege' anagrammed gives 'STRATEGIES'.

(Another definition for strategies that I've seen is " What planners need".)

I've seen this clue in The Times.

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