Regrets about long leads (5)
I believe the answer is:
rules
'leads' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps there's an association between them I don't understand?
'regrets about long' is the wordplay.
'regrets' becomes 'rues' ('rue' can be a synonym of 'regret').
'about' is an insertion indicator.
'long' becomes 'l'.
'rues' enclosing 'l' is 'RULES'.
Can you help me to learn more?
(Other definitions for rules that I've seen before include "In Australia, football" , "instructions" , "game in Australia" , "Reigns" , "following Queensberry?" .)