Full round in between (8)
I believe the answer is:
thorough
'full' is the definition.
(similar in meaning)
'round in between' is the wordplay.
'round' becomes 'o' (round can mean a round object).
'in' is an insertion indicator.
'between' becomes 'through'.
'o' put inside 'through' is 'THOROUGH'.
(Other definitions for thorough that I've seen before include "Painstaking; absolute" , "Total - painstaking - in-depth" , "Full" , "Careful, attending to every detail" , "Sweeping" .)