Bridge player must do this to dog clothes (6,4)
I believe the answer is:
follow suit
'bridge player must do this' is the definition.
The definition suggests a singular noun but the answer is not.
'dog clothes' is the wordplay.
'dog' becomes 'follow' (I've seen this before).
'clothes' becomes 'suit' (set of clothes).
'follow'+'suit'='FOLLOW SUIT'
'to' is the link.
Can you help me to learn more?
(Other definitions for follow suit that I've seen before include "Do the same as someone else" , "Do as others do" , "Play another club, perhaps" , "go from club to club" , "in due course" .)