Somehow be loud twice (6)
I believe the answer is:
double
'twice' is the definition.
(synonyms)
'somehow be loud' is the wordplay.
'somehow' indicates anagramming the letters.
'be'+'loud'='beloud'
'beloud' is an anagram of 'DOUBLE'.
(Other definitions for double that I've seen before include "Increase twofold" , "Bet - twice as much" , "Ringer - large drink" , "Twice - bent over - run" , "Orwellian acceptance of conflicting principles" .)