Like a GP sacked for being rusty? (3,2,8)
I believe the answer is:
out of practice
'being rusty?' is the definition.
(synonyms)
'like a gp sacked' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
'sacked' could be 'out' and 'out' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'for' is the link.
(Other definitions for out of practice that I've seen before include "being rusty?" , "Like a doctor dismissed" .)