Upsetting, short fuss from couple producing subscript (6)
I believe the answer is:
suffix
'subscript' is the definition.
(thesaurus)
'upsetting short fuss from couple' is the wordplay.
'upsetting' says the letters should be written backwards.
'short' means to remove the last letter.
'from' means one lot of letters go next to another.
'couple' becomes 'fix' (I can't explain this - if you can you should believe this answer much more).
'fuss' with its last letter removed is 'fus'.
'fus' back-to-front is 'suf'.
'suf'+'fix'='SUFFIX'
'producing' is the link.
Can you help me to learn more?
(Other definitions for suffix that I've seen before include "The 'ly' of 'badly'?" , "Letters added to the end of a word to form a derivative" , "End-of-word addition" , "Letter or letters added to the end to make another word" , "It's placed at the end of a word" .)