Foster development of many trees (6)
I believe the answer is:
forest
'of many trees' is the definition.
The definition suggests a singular noun which matches the answer.
'foster development' is the wordplay.
'development' indicates anagramming the letters.
'foster' is an anagram of 'FOREST'.
Can you help me to learn more?
(Other definitions for forest that I've seen before include "Thick growth of trees" , "Area thick with trees" , "eg Sherwood" , "Big wood" , "Sherwood or Pine, say" .)