Quite improper, old boy! An unseemly display (7)

I believe the answer is:

obscene

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'quite improper' is the definition.
'obscene' can be an answer for 'improper' (I've seen this before). I'm unsure of the 'quite' bit.

'old boy an unseemly display' is the wordplay.
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'an unseemly display' becomes 'scene' (I've seen this in another clue).
'ob'+'scene'='OBSCENE'

Can you help me to learn more?

(Other definitions for obscene that I've seen before include "Morally offensive, disgusting" , "offending sensibilities?" , "Highly offensive" , "Indecent or pornographic" , "Pseudonym" .)

I've seen this clue in the Evening Standard.

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