They take turns to provide transport two ways (5)
I believe the answer is:
vanes
'they take turns to' is the definition.
The definition suggests an adverb but the answer is not.
'transport two ways' is the wordplay.
'two ways' means two substitutions for 'way'.
'transport' becomes 'van' (van is a kind of transport).
'way' becomes 'e' (Compass direction - East).
'way' becomes 's' (Compass direction - South).
'van'+'e'+'s'='VANES'
'provide' acts as a link.
Can you help me to learn more?
(Other definitions for vanes that I've seen before include "Blades of windmill or propellers" , "Blades of a windmill or propeller" , "Weathercocks" , "Blades of a windmill (5)" , "Blades of a propellor or windmill sails" .)