Reduce some anguish or tension (7)
I believe the answer is:
shorten
'reduce' is the definition.
('shorten' can be a synonym of 'reduce')
'some anguish or tension' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'SHORTEN' is hidden within 'anguish or tension'.
(Other definitions for shorten that I've seen before include "Cut back" , "Truncate" , "Put extra fat" , "Prune" , "Abbreviate" .)