Declares a feeling of tension has returned (7)
I believe the answer is:
asserts
'declares' is the definition.
(asserting is a kind of declaring)
'a feeling of tension has returned' is the wordplay.
'a feeling' becomes 'stress' (I have seen 'Feeling of pressure' mean 'stress' so perhaps 'feeling' could also mean 'stress').
'of tension' becomes 'a' (I can't justify this - if you can you should give a lot more credence to this answer).
'has returned' says the letters should be written backwards.
'stress'+'a'='stressa'
'stressa' reversed gives 'ASSERTS'.
Can you help me to learn more?
(Other definitions for asserts that I've seen before include "Declares to be true" , "States categorically" , "States firmly" , "States confidently and forcefully" .)