Tramp working to fill-in for top person (7)
I believe the answer is:
monarch
'top person' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'tramp working to fill-in' is the wordplay.
'tramp' becomes 'march' (I've seen this in other clues).
'working' becomes 'on' (e.g. a machine is working or on).
'to fill in' indicates putting letters inside.
'march' enclosing 'on' is 'MONARCH'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for monarch that I've seen before include "Sovereign; butterfly" , "Eg, king, queen, emperor" , "Head of State" , "Butterfly - ruler" , "one over realm?" .)