Members of staff appear to backtrack over stratagem following closure of site (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Members of staff appear to backtrack over stratagem following closure of site <sit> E (“closure of” means last letter only) + [PLOY (=stratagem, ruse) in MEES (SEEM=appear; “to backtrack” indicates reversal)]