Five argue excitedly, becoming more unclear (6)
I believe the answer is:
vaguer
'more unclear' is the definition.
('vague' can be similar in meaning to 'unclear')
'five argue excitedly' is the wordplay.
'five' becomes 'V' (Roman numeral).
'excitedly' is an anagram indicator (letters excited or stimulated into a new form).
'argue' is an anagram of 'aguer'.
'v'+'aguer'='VAGUER'
'becoming' acts as a link.
(Other definitions for vaguer that I've seen before include "Less well defined" , "increasingly rough" .)