Tramp with a large rear end from Falkirk (4)
I believe the answer is:
walk
'tramp' is the definition.
(thesaurus)
'with a large rear end from falkirk' is the wordplay.
'with' is an insertion indicator.
'a large' becomes 'L' (eg in clothes sizes).
'rear' shows that the letters should be reversed in order (I've seen 'rearing' mean this (as in a horse rearing up)).
'end from falkirk' becomes 'kaw' (I can't justify this - if you can you should believe this answer much more).
'kaw' written backwards gives 'wak'.
'l' put inside 'wak' is 'WALK'.
Can you help me to learn more?
(Other definitions for walk that I've seen before include "Proceed on foot" , "Stretch one's legs" , "Amble" , "Go on foot" , "Perambulate" .)