Turn up on Sabbath to see Giants (5)
I believe the answer is:
ogres
'giants' is the definition.
(I know this)
'turn up on sabbath' is the wordplay.
'turn' becomes 'go' (a person's move in a board game).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'on' becomes 're' (regarding).
'sabbath' becomes 's'.
'go' reversed gives 'og'.
'og'+'re'+'s'='OGRES'
'to see' is the link.
(Other definitions for ogres that I've seen before include "Man-eating giants of folklore" , "Gorse (anag.)" , "Fairytale giants" , "Monstrous giants and man-eaters" , "'Monsters, fiends (5)'" .)