God with head surrounded by a circle (6)
I believe the answer is:
apollo
'god' is the definition.
(I've seen this before)
'head surrounded by a circle' is the wordplay.
'head' becomes 'poll' (poll is a now rare word for head or scalp**).
'surrounded by' means one lot of letters goes inside another.
'circle' becomes 'o'.
'a'+'o'='ao'
'poll' inserted into 'ao' is 'APOLLO'.
'with' is the link.
(Other definitions for apollo that I've seen before include "Greek god of light, poetry, music, healing and prophecy" , "US moon landing programme" , "Deity" , "US space program" , "mission of high-flying Americans?" .)