Laying out tenner, I grew a woodland plant (11)
I believe the answer is:
wintergreen
'a woodland plant' is the definition.
'wintergreen' can be an answer for 'plant' (wintergreen is a kind of plant). I'm not certain of the 'a woodland' bit.
'laying out tenner i grew' is the wordplay.
'laying out' indicates an anagram.
'tenner'+'i'+'grew'='tennerigrew'
'tennerigrew' is an anagram of 'WINTERGREEN'.
Can you help me to learn more?
(Other definitions for wintergreen that I've seen before include "for which golfers head around Christmas?" , "Medicinal plant oil" , "shrub" .)