Officiating at a square dance is a vocation (7)
I believe the answer is:
calling
'vocation' is the definition.
(synonyms)
'officiating at a square dance' is the wordplay.
I cannot really see how this works, but
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is located in the answer.
'a' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'is a' acts as a link.
Can you help me to learn more?
(Other definitions for calling that I've seen before include "visiting" , "Ringing" , "Vocation or profession" , "Urge to follow a particular career" , "Predicting the outcome" .)