Well up in a small department (5)

I believe the answer is:

adept

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'well up' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I don't see?

'a small department' is the wordplay.
'small department' becomes 'dept' (I am not sure about the 'small' bit.).
'a'+'dept'='ADEPT'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for adept that I've seen before include "One who is very skilful" , "Proficient, skilled" , "Proficient - expert" , "Handy" , "Completely skilled" .)

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

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