Rings up repeatedly for nothing special (2-2)
I believe the answer is:
so-so
'nothing special' is the definition.
(I've seen this before)
'rings up repeatedly' is the wordplay.
'rings' becomes 'os'.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'repeatedly' says to double the letters.
'os' reversed gives 'so'.
'so' doubled is 'SO-SO'.
'for' acts as a link.
(Other definitions for so-so that I've seen before include "Neither good nor bad" , "'Passable, middling (2-2)'" , "Rather middling" , "Fair to middling" , "Tolerable, indifferent" .)