Old boy spouts about traditional knick-knacks (6,4)
I believe the answer is:
objets dart
'knick-knacks' is the definition.
'old boy spouts about traditional' is the wordplay.
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'spouts' becomes 'jets' (I've seen this in another clue).
'about' is a reversal indicator.
'traditional' becomes 'trad' (abbreviation - especially in music 'trad jazz').
'trad' written backwards gives 'dart'.
'ob'+'jets'+'dart'='OBJETS DART'
(Other definitions for objets dart that I've seen before include "collectible items" , "decorative things" , "decorative little items" , "Small decorative items" .)