Guide to behaviour (7)
I believe the answer is:
conduct
I believe this clue is a double definition.
'guide' is the first definition.
('conduct' can be a synonym of 'guide')
'behaviour' is the second definition.
('conduct' can be a synonym of 'behaviour')
'to' acts as a link.
(Other definitions for conduct that I've seen before include "Behaviour; transmit" , "Guide - behaviour" .)