Dispute about a trendy Bohemian’s first colourful display (7)
I believe the answer is:
rainbow
'colourful display' is the definition.
(I've seen this before)
'dispute about a trendy bohemian's first' is the wordplay.
'dispute' becomes 'row' (row is a kind of dispute).
'about' means one lot of letters goes inside another.
'trendy' becomes 'in' ('in' can mean fashionable).
'bohemian's first' becomes 'b' (1st letter of 'bohemian').
'a'+'in'+'b'='ainb'
'row' going around 'ainb' is 'RAINBOW'.
(Other definitions for rainbow that I've seen before include "Arc of colours" , "an impossible dream being chased?" , "Light effect in sky" , "Multi-coloured arch" , "Arc of colored light in the sky" .)