A section expert (5)

I believe the answer is:

adept

'expert' is the definition.
(adept is a kind of expert)

'a section' is the wordplay.
'section' becomes 'dept' (short for department).
'a'+'dept'='ADEPT'

(Other definitions for adept that I've seen before include "Skillful" , "One very skilled at work" , "Having the skill required" , "efficient" , "who gets the lapis philosophicus secret" .)

I've seen this clue in The Independent.

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