Endlessly awkward old man responsible for stock (6)
I believe the answer is:
gaucho
'man responsible for stock' is the definition.
'endlessly awkward old' is the wordplay.
'endlessly' means to remove the last letter.
'awkward' becomes 'gauche' (I've seen this before).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'gauche' with its last letter taken off is 'gauch'.
'gauch'+'o'='GAUCHO'
(Other definitions for gaucho that I've seen before include "Surprise attacker" , "Horseman of the S American plains" , "Ranch hand" , "plainsman" , "Horseman of the Pampas" .)