Ring up about special work (4)
I believe the answer is:
opus
'work' is the definition.
(an opus is an artistic work)
'ring up about special' is the wordplay.
'ring' becomes 'o' (letter resembling a ring).
'about' says the letters should be written backwards.
'special' becomes 'S' (common abbreviation as in Special Air Service).
'up' in reverse letter order is 'pu'.
'o'+'pu'+'s'='OPUS'
(Other definitions for opus that I've seen before include "Major work" , "Composition - magnum __" , "A Latin work" , "(Numbered) musical composition" , "Work (of a composer?)" .)