Area regularly guarded by mean, threatening fish (8)
I believe the answer is:
stingray
'threatening fish' is the definition.
'stingray' can be an answer for 'fish' (type of fish). I am not certain of the 'threatening' bit.
'area regularly guarded by mean' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'guarded by' means one lot of letters goes inside another.
'mean' becomes 'stingy' (both can mean miserly).
The alternate letters of 'area' are 'ra'.
'ra' put into 'stingy' is 'STINGRAY'.
Can you help me to learn more?
(Other definitions for stingray that I've seen before include "Dangerous fish" , "TV show" , "menace in the water" , "Poisonous spined fish" , "Marine creature with venomous tail" .)