Fashion associated with posh doctor occasioning offence (7)
I believe the answer is:
umbrage
'offence' is the definition.
(I've seen this before)
'fashion associated with posh doctor' is the wordplay.
'fashion' becomes 'rage' (rage is a kind of fashion**).
'associated with' says to put letters next to each other.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-u).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'u'+'mb'='umb'
'rage' after 'umb' is 'UMBRAGE'.
'occasioning' acts as a link.
(Other definitions for umbrage that I've seen before include "Indignation" , "Displeasure" , "The sulks" , "In high dudgeon" , "Take this to be offended" .)