A pupil, with precipitation, enters the stand (7)
I believe the answer is:
trainee
'a pupil' is the definition.
(thesaurus)
'precipitation enters the stand' is the wordplay.
'precipitation' becomes 'rain' (rain is a kind of precipitation).
'enters' is an insertion indicator.
'the stand' becomes 'tee' (I've seen this before).
'rain' put within 'tee' is 'TRAINEE'.
'with' acts as a link.
(Other definitions for trainee that I've seen before include "One learning a job" , "One being instructed" , "Person being taught" , "one not yet qualified" , "Apprentice" .)