Move around cast-iron brackets (4)
I believe the answer is:
stir
'move around' is the definition.
(synonyms)
'cast-iron brackets' is the wordplay.
'brackets' indicates the answer is hidden within the clue (the answer is contained or bracketed by the clue).
'STIR' is hidden in the letters of 'cast iron'.
(Other definitions for stir that I've seen before include "Rouse; prison (colloq.)" , "Wake up - prison" , "Excitement" , "Whisk or mix" , "Arouse; mix" .)