Apprentice gunners at home entertained by Peg (7)
I believe the answer is:
trainee
'apprentice' is the definition.
(I've seen this before)
'gunners at home entertained by peg' is the wordplay.
'gunners' becomes 'ra' (Royal Artillery).
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'entertained by' means one lot of letters goes inside another (I've seen this in other clues).
'peg' becomes 'tee' (tee is a kind of peg).
'ra'+'in'='rain'
'rain' placed into 'tee' is 'TRAINEE'.
(Other definitions for trainee that I've seen before include "One being taught a job" , "encountered bad weather in driving area" , "As pupil" , "New recruit" , "A beginner in Aintree" .)