Attempted to gobble pie up outside United’s ground (10)

'ground' is the definition.
(thesaurus)

'attempted to gobble pie up outside united's' is the wordplay.
'attempted' becomes 'tried' ('try' can be a synonym of 'attempt').
'to gobble' indicates putting letters inside.
'pie up' becomes 'trat' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'outside' means one lot of letters goes inside another.
'united' becomes 'U' (abbreviation).
'tried' enclosing 'trat' is 'tritrated'.
'tritrated' placed around 'u' is 'TRITURATED'.

Can you help me to learn more?