Swineherd a Yankee in celebration (8)
I believe the answer is:
hogmanay
'celebration' is the definition.
(I've seen this before)
'swineherd a yankee' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is found in the answer.
'yankee' could be 'y' (phonetic alphabet: alpha, bravo, charlie etc.) and 'y' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for hogmanay that I've seen before include "New Year's Eve in Glasgow" , "Scottish celebration framed in mahogany" , "Festival" , "New Year's Eve (Scots)" , "today" .)