Acknowledged grass is necessary around small garden feature (9)
I believe the answer is:
responded
'acknowledged' is the definition.
The answer and definition can be both related to thinking as well as being past participle verbs.
Maybe you can see an association between them that I can't see?
'grass is necessary around small garden feature' is the wordplay.
'grass' becomes 'reed' (I've seen this before).
'is necessary' is an insertion indicator.
'around small' becomes 's' (abbreviation - e.g. clothes size. I am not sure about the 'around' bit.**).
'garden feature' becomes 'pond'.
's'+'pond'='spond'
'reed' going around 'spond' is 'RESPONDED'.
Can you help me to learn more?
(Other definitions for responded that I've seen before include "Replied, reacted" , "Came back" , "Answered or reacted" .)