Alert cops develop muscles (9)

I believe the answer is:

pectorals

'muscles' is the definition.
(pectoral is a kind of muscle)

'alert cops develop' is the wordplay.
'develop' indicates an anagram.
'alert'+'cops'='alertcops'
'alertcops' anagrammed gives 'PECTORALS'.

(Another definition for pectorals that I've seen is " Muscles".)

I've seen this clue in The Telegraph.

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