Was of service when a few were sick (7)

I believe the answer is:

availed

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'was of service' is the definition.
I can't tell whether this definition defines the answer.

'a few were sick' is the wordplay.
'few' becomes 'v'.
'were sick' becomes 'ailed' ('ail' can be a synonym of 'be sick').
'a'+'v'+'ailed'='AVAILED'

'when' acts as a link.

Can you help me to learn more?

(Other definitions for availed that I've seen before include "Profited from" , "Helped" , "Used to one's advantage" , "Used, put into service" .)

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

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