Travel free on first excursion (4)
I believe the answer is:
ride
'travel' is the definition.
(riding is a kind of travelling)
'free on first excursion' is the wordplay.
'free' becomes 'rid' ('rid' can be a synonym of 'free'**).
'on' says to put letters next to each other.
'first' indicates taking the first letters.
The initial letter of 'excursion' is 'e'.
'rid'+'e'='RIDE'
(Other definitions for ride that I've seen before include "Travel upon" , "Fairground attraction; go on horseback" , "What suckers are taken for" , "Sally" , "Travel, on horseback, say" .)