Supporter of a high standard, perhaps (4)
I believe the answer is:
mast
'supporter' is the definition.
(thesaurus)
'a high standard perhaps' is the wordplay.
I cannot really understand how this works, but
'a' is found in the answer.
The remaining letters 'mst' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for mast that I've seen before include "Pole aboard; fruit for pigs" , "Supporting pole, for radio aerial, perhaps" , "Pole supporting ship's sails" , "Long upright pole that supports sails" , "Pole to support a sail" .)