Designer chap has odd air about him (6)
I believe the answer is:
armani
'designer' is the definition.
(I've seen this before)
'odd air about him' is the wordplay.
'odd' means one should take alternating letters.
'about' is a charade indicator (letters next to each other).
'him' becomes 'arman' ().
The alternating letters of 'air' are 'i'.
'i' put after 'arman' is 'ARMANI'.
'chap has' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for armani that I've seen before include "suit perhaps" , "Italian fashion house" , "Giorgio -, It. designer" , "famous fashion designer" .)