By playing three of diamonds one indicated support (6)
I believe the answer is:
nodded
'by playing three of diamonds' is the definition.
I can't judge whether this defines the answer.
'one indicated support' is the wordplay.
I cannot quite see how this works, but
'one' could be 'odd' (I've seen this before) and 'odd' is found in the answer.
The remaining letters 'ned' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nodded that I've seen before include "Let the head drop" , "Signalled yes" , "Moved head as in consent" , "Indicated assent with head movement" , "Made a mistake" .)