A Yardie's ground, supposedly (1,4,3)
I believe the answer is:
i dare say
'supposedly' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'a yardie's ground' is the wordplay.
'ground' is an anagram indicator ('grind' the letters into a new form).
'a'+'yardies'='ayardies'
'ayardies' anagrammed gives 'I DARE SAY'.
Can you help me to learn more?
(Other definitions for i dare say that I've seen before include "It is probable" , "one might suppose" , "Quite possibly" , "Probably" , "It wouldn't surprise me" .)