Before Sabbath former head of state visits school grounds (8)
I believe the answer is:
terrains
'grounds' is the definition.
(I've seen this in another clue)
'before sabbath former head of state visits school' is the wordplay.
'before' means one lot of letters go next to another.
'sabbath' becomes 's'.
'former head of state' becomes 'ER' (Elizabeth Regina, ie Queen Elizabeth).
'visits' is an insertion indicator (inserted letters visit the inside of another word).
'school' becomes 'train' (school can mean to train or coach).
'er' going inside 'train' is 'terrain'.
's' after 'terrain' is 'TERRAINS'.
(Other definitions for terrains that I've seen before include "countries" , "Areas of land" .)