Dreads becoming more unhappy (6)
I believe the answer is:
sadder
'more unhappy' is the definition.
('sad' can be similar in meaning to 'unhappy')
'dreads becoming' is the wordplay.
'becoming' is an anagram indicator.
'dreads' anagrammed gives 'SADDER'.
(Other definitions for sadder that I've seen before include "extra-blue?" , "more blue" , "Lower" , "More downcast" , "Unhappier" .)