Line right in account (3)
I believe the answer is:
arc
'line' is the definition.
(I know that line can be written as arc)
'right in account' is the wordplay.
'right' becomes 'r' (common abbreviation).
'in' indicates putting letters inside.
'account' becomes 'ac' (abbreviation for account).
'r' going within 'ac' is 'ARC'.
(Other definitions for arc that I've seen before include "Light" , "Something curved in shape" , "Section of circumference" , "Curved section" , "Curvature" .)