Choice to turn it on after surgery (6)
I believe the answer is:
option
'choice' is the definition.
('option' can be a synonym of 'choice')
'turn it on after surgery' is the wordplay.
'turn' says the letters should be written backwards.
'after' says to put letters next to each other.
'surgery' becomes 'op' (short for operation).
'it' written backwards gives 'ti'.
'ti'+'on'='tion'
'tion' put after 'op' is 'OPTION'.
'to' is the link.
(Other definitions for option that I've seen before include "Choice, selection" , "Right to choose" , "Possible choice" , "possibility" , "Alternative for choice" .)