A direction? Let it stand in the last six lines (6)
I believe the answer is:
sestet
'last six lines' is the definition.
The answer and definition can be both quantities as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'a direction? let it stand' is the wordplay.
'a direction?' becomes 'SE' (SE is an example).
'let it stand' becomes 'stet' (I've seen this before).
'se'+'stet'='SESTET'
'in the' is the link.
Can you help me to learn more?
(Other definitions for sestet that I've seen before include "Group of six" , "Six together" , "musical ensemble" , "Set of six performers" , "Tsetse (anag.)" .)