Playing card incorporating old-fashioned diamonds is familiar (10)
I believe the answer is:
acquainted
'familiar' is the definition.
(similar in meaning)
'playing card incorporating old-fashioned diamonds' is the wordplay.
'playing card' becomes 'ace' (ace is a kind of playing card).
'incorporating' indicates putting letters inside.
'old-fashioned' becomes 'quaint' (cutely old-fashioned).
'diamonds' becomes 'd' (abbreviation in bridge say).
'ace' going around 'quaint' is 'acquainte'.
'acquainte'+'d'='ACQUAINTED'
'is' is the link.
(Other definitions for acquainted that I've seen before include "Notified" , "Well-versed" , "Made aware of" , "Familiar (with)" , "on good terms" .)