Answered that reeds spread around a source of water (9)
I believe the answer is:
responded
'answered' is the definition.
('respond' can be a synonym of 'answer')
'reeds spread around a source of water' is the wordplay.
'spread' indicates an anagram.
'around' is an insertion indicator.
'a source of water' becomes 'pond' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'reeds' is an anagram of 'resed'.
'resed' going around 'pond' is 'RESPONDED'.
'that' acts as a link.
Can you help me to learn more?
(Other definitions for responded that I've seen before include "Came back" , "Answered or reacted" , "Replied, reacted" .)