Predecessor is dreadfully decent and neat (10)
I believe the answer is:
antecedent
'predecessor' is the definition.
(I've seen this in another clue)
'dreadfully decent and neat' is the wordplay.
'dreadfully' indicates anagramming the letters (a dreadful spelling).
'and' means one lot of letters go next to another.
'decent' after 'neat' is 'neatdecent'.
'neatdecent' with letters rearranged gives 'ANTECEDENT'.
'is' is the link.
(Other definitions for antecedent that I've seen before include "prior" , "Previous" , "Something previously extant" , "Something existing before another" , "Going before (in time/order)" .)