Brief excursion to hit pay dirt (3,4)
I believe the answer is:
day trip
'brief excursion' is the definition.
(I've seen this before)
'hit pay dirt' is the wordplay.
'hit' indicates anagramming the letters.
'pay'+'dirt'='paydirt'
'paydirt' is an anagram of 'DAY TRIP'.
'to' acts as a link.
(Other definitions for day trip that I've seen before include "Brief excursion" , "Pay dirt (anag.)" , "Outing" , "Excursion within 24 hours" .)