Don't move support placed in position (4,3)
I believe the answer is:
stay put
'don't move' is the definition.
(I've seen this in another clue)
'support placed in position' is the wordplay.
I cannot really understand how this works, but
'support' could be 'stay' (stay is a kind of support) and 'stay' is found in the answer.
'placed' could be 'put' (I've seen this before) and 'put' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stay put that I've seen before include "Stick around" , "Informally, don't move - remain in situ" , "Remain unmoving" , "Remain in place, don't move" , "Remain in one place" .)