Monty, taking a wild pony round Southend (6)
I believe the answer is:
python
'monty' is the definition.
I can't tell whether this defines the answer.
'a wild pony round southend' is the wordplay.
'a wild' is an anagram indicator.
'round' indicates putting letters inside.
'southend' becomes 'th' (I can't explain this - if you can you should believe this answer much more).
'pony' is an anagram of 'pyon'.
'pyon' going around 'th' is 'PYTHON'.
'taking' is the link.
Can you help me to learn more?
(Other definitions for python that I've seen before include "Type of snake" , "Snake that kills its prey by squeezing" , "Dragon killed by Apollo at Delphi" , "Large snake that kills prey by crushing" , "Big snake that crushes its prey" .)