Staff outside gallery took turns (7)
I believe the answer is:
Here is my best explanation:
'took turns' is the definition.
(rotating is a kind of taking turns)
'staff outside gallery' is the subsidiary indication.
'staff' becomes 'rod' (I've seen this before).
'outside' is an insertion indicator.
'gallery' becomes 'tate'.
'rod' enclosing 'tate' is 'rotated'.
(Other definitions for rotated that I've seen before include "Spun", "took part in revolution", "Turner did?", "Had spin", "Turned round", "Revolved", "Turned around axis or central point", "spun", "Went round" and "Turned in a circle around an axis".)