Ultimately, wad super fat (8)
I believe the answer is:
dripping
'fat' is the definition.
(dripping is a kind of fat)
'ultimately wad super' is the wordplay.
'ultimately' says to take the final letters.
'super' becomes 'ripping' (old-fashioned informal term for excellent).
The final letter of 'wad' is 'd'.
'd'+'ripping'='DRIPPING'
(Other definitions for dripping that I've seen before include "Very wet; fat from roast" , "Saturated" , "tap needing washer?" , "sweaty" , "F [FAT]" .)