Six lines of poetry set around a time standard (6)
I believe the answer is:
sestet
'six' is the definition.
(synonyms)
'around a time standard' is the wordplay.
'around' is an insertion indicator.
'a time' becomes 'est' (EST is an example).
'standard' becomes 'set'.
'est' going into 'set' is 'SESTET'.
'lines of poetry set' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sestet that I've seen before include "Set of six performers" , "Six together" , "Tsetse (anag.)" , "musical ensemble" , "Group of six" .)