Endlessly awkward old South American cowboy (6)
I believe the answer is:
gaucho
'south american cowboy' is the definition.
(I've seen this before)
'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 "Plain-living person" , "A cough (anag)" , "Argentinian cattle-herder" , "Cowboy of Argentine's plains" , "foreign cowhand" .)