One said to swear or turn into a drunkard (7)

I believe the answer is:

trooper

I'm a little stuck... Click here to teach me more about this clue!

'one said to swear' is the definition.
I can't judge whether this defines the answer.

'or turn into a drunkard' is the wordplay.
'turn' indicates anagramming the letters.
'into' is an insertion indicator.
'a drunkard' becomes 'toper' (I've seen this in another clue).
'or' with letters rearranged gives 'ro'.
'ro' going within 'toper' is 'TROOPER'.

Can you help me to learn more?

(Other definitions for trooper that I've seen before include "He swears" , "Cavalry soldier" , "Private soldier" , "ship" , "Soldier, proverbial swearer" .)

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

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