The mounties have to join, of course (3)
I believe the answer is:
tie
'join of course' is the definition.
'tie' can be an answer for 'join' (tie can mean to connect or join together). I'm unsure of the 'of course' bit.
'the mounties have' is the wordplay.
'have' indicates a hidden word.
'TIE' can be found hidden inside 'mounties'.
'to' is the link.
Can you help me to learn more?
(Other definitions for tie that I've seen before include "Knot; limit" , "A draw or male neckwear" , "Fasten; draw" , "Form into a knot or bow" , "Encumbrance" .)