Eager to have knee operation (4)
I believe the answer is:
keen
'eager' is the definition.
(I've seen this before)
'have knee operation' is the wordplay.
'knee' can be anagrammed to 'KEEN'.
However, I'm not clear how this is indicated.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for keen that I've seen before include "Anxious" , "Acute" , "Fierce - sharp" , "Having a fine edge to weep over the dead" , "Sharp - avid" .)