Old volunteers with Oxfam, say, getting letter from NATO (5)
I believe the answer is:
tango
'letter from nato' is the definition.
(NATO phonetic alphabet)
'old volunteers with oxfam say' is the wordplay.
I cannot really see how this works, but
'old' could be 'o' (abbreviation) and 'o' is found in the answer.
'volunteers' could be 'ta' (abbreviation for Territorial Army) and 'ta' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'getting' acts as a link.
Can you help me to learn more?
(Other definitions for tango that I've seen before include "Latin-American dance - code for T" , "Last - in Paris (film)" , "reputedly takes two" , "Argentine dance" , "Steps" .)