Petty guy has to trim lawn round the pub (6)
I believe the answer is:
minnow
'petty guy' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'to trim lawn round the pub' is the wordplay.
'to trim lawn' becomes 'mow' (I am not sure about this - if you are sure you should believe this answer much more).
'round' is an insertion indicator.
'the pub' becomes 'inn' (an inn is a type of pub).
'mow' placed around 'inn' is 'MINNOW'.
'has' is the link.
Can you help me to learn more?
(Other definitions for minnow that I've seen before include "Tiny freshwater fish" , "Tiddler" , "Little person" , "unimportant person" , "Very little fish" .)