Army recruits discontented mariners (4)

I believe the answer is:

tars

'mariners' is the definition.
(I know this)

'army recruits discontented' is the wordplay.
'army' becomes 'TA' (abbreviation for Territorial Army).
'discontented' means to remove the middle letters (the word's contents are removed).
'recruits' with its middle removed is 'rs'.
'ta'+'rs'='TARS'

(Another definition for tars that I've seen is " Sailors".)

I've seen this clue in The Independent.

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