Figure old motor starter is installed in right-hand vehicle (7)
I believe the answer is:
rhombus
'figure' is the definition.
(I know that rhombus is a type of parallelogram)
'old motor starter is installed in right-hand vehicle' is the wordplay.
'starter' suggests taking the first letters.
'is installed in' indicates putting letters inside.
'right hand' becomes 'RH' (medical abbreviation).
'vehicle' becomes 'bus' (bus is a kind of vehicle).
The initial letters of 'old motor' is 'om'.
'rh'+'bus'='rhbus'
'om' going inside 'rhbus' is 'RHOMBUS'.
(Other definitions for rhombus that I've seen before include "Large bottle; vessel with spout" , "Quadrilateral with four equal sides" , "Regular parallelogram" , "Diamond shape" , "Form of quadrilateral" .)