Though brown, this pool has a red strip (5)
I believe the answer is:
liver
'though brown this' is the definition.
The definition suggests a singular noun which matches the answer.
'pool has a red strip' is the wordplay.
'pool has' becomes 'liv' (I can't justify this - if you can you should give a lot more credence to this answer).
'a red' becomes 'cherry' (cherry is a kind of red).
'strip' says to take the centre (I've seen 'stripped' mean this).
The middle of 'cherry' is 'er'.
'liv'+'er'='LIVER'
Can you help me to learn more?
(Other definitions for liver that I've seen before include "Abdominal organ" , "Human organ" , "Hepatic organ" , "Bodily organ" , "Bile-secreting organ" .)