Guy wants old variety for shrub (4,6)
I believe the answer is:
mock orange
'shrub' is the definition.
(mock orange is a kind of shrub)
'guy wants old variety' is the wordplay.
'guy' becomes 'mock' (both can mean to make fun of).
'wants' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'variety' becomes 'range' (range can mean a wide variety).
'mock'+'o'+'range'='MOCK ORANGE'
'for' is the link.
(Other definitions for mock orange that I've seen before include "Philadelphus (popularly syringa)" , "plant" , "bush" , "Scented shrub" , "Shrub with fragrant white flowers" .)