Gun, shot in extremity, giving voice (6)
I believe the answer is:
tongue
'voice' is the definition.
(thesaurus)
'gun shot in extremity' is the wordplay.
'shot' indicates an anagram.
'in' indicates putting letters inside.
'extremity' becomes 'toe' (toe is a kind of extremity**).
'gun' with letters rearranged gives 'ngu'.
'ngu' inserted into 'toe' is 'TONGUE'.
'giving' acts as a link.
(Other definitions for tongue that I've seen before include "Speech" , "Perhaps the Gaelic" , "Projecting strip" , "Ability to speak - a language" , "Muscular tissue in the mouth" .)