Male to speak or mumble (6)
I believe the answer is:
mutter
'mumble' is the definition.
(I know that mumble can be written as mutter)
'male to speak' is the wordplay.
'male' becomes 'm' (common abbreviation).
'to speak' becomes 'utter' ('utter' can be a synonym of 'speak').
'm'+'utter'='MUTTER'
'or' acts as a link.
(Other definitions for mutter that I've seen before include "Speak quietly and indistinctly" , "Barely audible utterance" , "German violinist" , "Grumble in secret; mother (German)" , "Speak indistinctly or grumble" .)