Apply in a pert sort of way? (7)

I believe the answer is:

pertain

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'apply' is the definition.
(I know that apply is a more specific form of the action pertain)

'a pert sort of way?' is the wordplay.
'sort' is an anagram indicator.
'of way?' becomes 'in' (I can't explain this - if you can you should give a lot more credence to this answer).
'a'+'pert'='apert'
'apert' is an anagram of 'perta'.
'perta'+'in'='PERTAIN'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for pertain that I've seen before include "Relate (to), apply (to)" , "Painter (anag) - relate (to)" , "Be relevant, or belong as part" , "Have relevance" , "Refer" .)

I've seen this clue in the Evening Standard.

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