Terribly ill in quarters, squaddie initially gets drugs (14)

I believe the answer is:

tranquillisers

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'drugs' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'terribly ill in quarters squaddie initially' is the wordplay.
'terribly' indicates anagramming the letters.
'initially' indicates taking the first letters.
The initial letter of 'squaddie' is 's'.
'ill'+'in'+'quarters'='illinquarters'
'illinquarters' anagrammed gives 'tranquilliser'.
'tranquilliser'+'s'='TRANQUILLISERS'

'gets' acts as a link.

Can you help me to learn more?

(Another definition for tranquillisers that I've seen is " shifting drugs".)

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