Sally follows a direction to arm (5)
I believe the answer is:
equip
'arm' is the definition.
(arm can mean to equip or supply)
'sally follows a direction' is the wordplay.
'sally' becomes 'quip' (both can mean a witty remark).
'follows' means one lot of letters go next to another.
'a direction' becomes 'e' (E is an example).
'quip' after 'e' is 'EQUIP'.
'to' acts as a link.
(Other definitions for equip that I've seen before include "Fit out, supply" , "Give kit to" , "Furnish with supplies" , "Accoutre" , "Supply tools" .)