Stick to one part of your argument (3)
I believe the answer is:
gum
'stick' is the definition.
(gum can mean to glue or stick)
'one part of your argument' is the wordplay.
'one part of' indicates a hidden word.
'GUM' can be found hidden inside 'your argument'.
'to' acts as a link.
(Other definitions for gum that I've seen before include "Gingeva is its technical name" , "surrounding roots of teeth?" , "Glue; jelly-like sweet" , "Stuff to chew" , "Eg, a eucalyptus" .)