Mug holding seconds - it risks getting bust (5)
I believe the answer is:
twist
'it risks getting bust' is the definition.
The definition suggests a singular noun which matches the answer.
'mug holding seconds' is the wordplay.
'mug' becomes 'twit' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'holding' indicates putting letters inside.
'seconds' becomes 's' (abbreviation).
'twit' placed around 's' is 'TWIST'.
Can you help me to learn more?
(Other definitions for twist that I've seen before include "Wind round - distort" , "Screw; distort" , "Wrench, distort" , "Wind spirally" , "Spiral" .)