They send up runners to welcome leading lady (6)
I believe the answer is:
skiers
'they send up' is the definition.
(to sky is to hit something into the sky)
'runners to welcome leading lady' is the wordplay.
'runners' becomes 'skis' (ski is a kind of runner).
'to welcome' means one lot of letters goes inside another (in sense of 'inviting in').
'leading lady' becomes 'er' (Elizabeth Regina).
'skis' enclosing 'er' is 'SKIERS'.
(Other definitions for skiers that I've seen before include "They glide on the piste" , "Winter sportsmen" , "Kisser among snow sportsmen" , "Persons on the slopes" , "aerial shots" .)