Speaking wildly in gutter (8)
I believe the answer is:
uttering
'speaking' is the definition.
('utter' can be a synonym of 'speak')
'wildly in gutter' is the wordplay.
'wildly' indicates an anagram.
'in'+'gutter'='ingutter'
'ingutter' is an anagram of 'UTTERING'.
(Other definitions for uttering that I've seen before include "Tiger-nut (anag.)" , "Saying" , "Publishing" , "Articulating" .)