Sign agreement to put on turns (3)
I believe the answer is:
nod
'sign agreement' is the definition.
(I've seen this before)
'put on turns' is the wordplay.
'put on' becomes 'don' (as in donning or putting on an item of clothing).
'turns' says the letters should be written backwards.
'don' reversed gives 'NOD'.
'to' is the link.
(Other definitions for nod that I've seen before include "Bob the head" , "Appear to fall asleep" , "Silent assent" , "Show assent" , "Signify consent" .)