The Earth perhaps concerned with energy growth (5,4)
I believe the answer is:
plane tree
'growth' is the definition.
(I've seen this before)
'the earth perhaps concerned with energy' is the wordplay.
'the earth perhaps' becomes 'planet' (Earth is an example).
'concerned with' becomes 're' (re can mean regarding, concerning).
'energy' becomes 'e' (physics symbol as in E=mc2).
'planet'+'re'+'e'='PLANE-TREE'
(Other definitions for plane tree that I've seen before include "growth" , "Common city plant" , "maple" , "It sheds its bark" .)