Rider is very poor on the move (7)
I believe the answer is:
proviso
'rider' is the definition.
(I've seen this before)
'is very poor on the move' is the wordplay.
'very' becomes 'v' (abbreviation).
'on the move' indicates anagramming the letters.
'is'+'v'+'poor'='isvpoor'
'isvpoor' with letters rearranged gives 'PROVISO'.
(Other definitions for proviso that I've seen before include "Requirement" , "Stipulated condition" , "Something insisted upon as part of an agreement" , "Condition, qualification" , "Condition of stipulation of an agreement" .)