Holiday job initially involves a day trip to Saudi (4)

I believe the answer is:
hadj
'trip to saudi' is the definition.
I can't tell whether this definition defines the answer.
'holiday job initially involves a day' is the wordplay.
'initially' indicates taking the first letters.
'involves' means one lot of letters goes inside another.
'day' becomes 'd' (abbreviation for day).
The first letters of 'holiday job' is 'hj'.
'a'+'d'='ad'
'hj' placed around 'ad' is 'HADJ'.
Can you help me to learn more?
(Other definitions for hadj that I've seen before include "A pilgrimage to Mecca, duty of Muslims" , "Once in a lifetime experience, perhaps" , "once-in-a-lifetime trip?" , "Spiritual trip" , "One pillar" .)
