Son of gardener, one with a shrub (6)
I believe the answer is:
abelia
'shrub' is the definition.
(abelia is a kind of shrub)
'son of gardener one with a' is the wordplay.
'son of gardener' becomes 'Abel' (son of Adam from the Bible, 'the first gardener').
'one' becomes 'i' (Roman numeral).
'with' says to put letters next to each other.
'abel'+'i'+'a'='ABELIA'
(Other definitions for abelia that I've seen before include "shrub" , "Honeysuckle" , "plant" .)