Old boy reportedly perceived to be off-colour (7)
I believe the answer is:
obscene
'off-colour' is the definition.
Both the definition and answer are adjectives.
Perhaps there's a link between them I don't understand?
'old boy reportedly perceived' is the wordplay.
'old boy' becomes 'ob'.
'reportedly' indicates a 'sounds like' (homophone) clue.
'perceived' becomes 'seen' (I've seen this before).
'seen' sounds like 'scene'.
'ob'+'scene'='OBSCENE'
'to be' is the link.
Can you help me to learn more?
(Other definitions for obscene that I've seen before include "Disgusting, repugnant" , "coarse!" , "Offensive - indecent" , "Pseudonym" , "Lewd - offensive" .)