Guards ordered to breached lines (9)

I believe the answer is:

sentinels

'guards' is the definition.
(sentinel is a kind of guard)

'ordered to breached lines' is the wordplay.
'ordered' becomes 'sent'.
'to breached' becomes 'in' (I've seen this in other clues).
'lines' becomes 'els' (el is a kind of line).
'sent'+'in'+'els'='SENTINELS'

(Another definition for sentinels that I've seen is " Lookout men".)

I've seen this clue in The Globe and Mail.

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