It's a lot different on Tuesday, that's all (5)
I believe the answer is:
total
'that's all' is the definition.
(thesaurus)
'it's a lot different on' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'different' is an anagram indicator.
'on' means one lot of letters goes inside another (as in clothing 'on' a person).
'lot' anagrammed gives 'otl'.
'a' placed into 'otl' is 'otal'.
't'+'otal'='TOTAL'
'tuesday' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for total that I've seen before include "It might be grand" , "Aggregate amount" , "to give the final figure" , "Entirety" , "Come to" .)