The first tear in the excursion (4)
I believe the answer is:
trip
'the excursion' is the definition.
(a trip is an excursion or outing)
'the first tear' is the wordplay.
'the first' becomes 't' (1st letter of 'the').
'tear' becomes 'rip' (synonyms).
't'+'rip'='TRIP'
'in' is the link.
(Other definitions for trip that I've seen before include "Pleasure excursion" , "Set off for" , "Accidental misstep" , "In close confrontation" , "Outing; stumble" .)