Branch of 1 Ac. in Brazil surrounded by aquatic organisms with a twisted tail (7)
I believe the answer is:
algebra
'branch' is the definition.
(I have seen 'Branch of mathematics' mean 'algebra' so perhaps 'branch' could also mean 'algebra')
'1 ac in brazil surrounded by aquatic organisms with a twisted tail' is the wordplay.
I cannot really understand how this works, but
'1' could be 'a' (both can mean one) and 'a' is found within the answer.
'brazil' could be 'br' and 'br' is located in the answer.
'a' is present in the answer.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for algebra that I've seen before include "letters here set out the problem" , "Part of mathematics" , "Numbers and letters branch of maths" , "Maths with letters representing numbers" , "Symbol-based mathematical calculation" .)