Bearing gun going round island (4)
I believe the answer is:
gait
'bearing' is the definition.
(I've seen this before)
'gun going round island' is the wordplay.
'gun' becomes 'gat' (gat is a kind of gun).
'going round' is an insertion indicator.
'island' becomes 'i'.
'gat' enclosing 'i' is 'GAIT'.
(Other definitions for gait that I've seen before include "walkway?" , "Way of walking (4)" , "Carriage" , "Bearing" , "Method of moving" .)