Specific terms obtained by gutless ambassador (5)
I believe the answer is:
argot
'specific terms' is the definition.
(argot means a sort of jargon)
'obtained by gutless ambassador' is the wordplay.
'obtained' becomes 'got' ('get' can be a synonym of 'obtain').
'by' is a charade indicator (letters next to each other).
'gutless' suggests removing the centre.
'ambassador' with its centre removed is 'ar'.
'got' after 'ar' is 'ARGOT'.
(Other definitions for argot that I've seen before include "Specialised language" , "Particular group's jargon" , "Ancient Greek coin" , "Slang for a groat (5)" , "Patois, vernacular" .)