Fat sign of faulty tap (8)
I believe the answer is:
dripping
'fat' is the definition.
(dripping is a kind of fat)
'sign of faulty tap' is the wordplay.
I cannot quite see how this works, but
'sign' could be 'pin' (pin is a kind of sign) and 'pin' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for dripping that I've seen before include "Fat melted from roasted meat" , "Very wet; fat from roast" , "sweaty" , "tap needing washer?" , "Saturated" .)