Charge when admitting first of tourists for outdoor event (4)
I believe the answer is:
fete
'outdoor event' is the definition.
(I've seen this before)
'charge when admitting first of tourists' is the wordplay.
'charge when' becomes 'fee' (fee is a kind of charge. I am not sure about the 'when' bit.**).
'admitting' is an insertion indicator.
'first of' says to take the initial letters.
The first letter of 'tourists' is 't'.
'fee' enclosing 't' is 'FETE'.
'for' acts as a link.
(Other definitions for fete that I've seen before include "Outdoor fundraiser" , "Outdoor festival" , "Outdoor entertainment run for charity" , "Organised series of acts and performances" , "Lavishly entertain; charity function" .)