Senior judge and upper-class politician bound to compete in this (4,4)
I believe the answer is:
high jump
'bound to compete in this' is the definition.
The definition suggests a singular noun which matches the answer.
'senior judge and upper-class politician' is the wordplay.
'senior' becomes 'high' (I can't explain this - if you can you should give a lot more credence to this answer).
'judge' becomes 'J' (abbreviation for judge).
'and' says to put letters next to each other.
'upper class' becomes 'u' (as in U- and non-U speech).
'politician' becomes 'MP' (Member of Parliament).
'high'+'j'+'u'+'mp'='HIGH JUMP'
Can you help me to learn more?
(Other definitions for high jump that I've seen before include "A severe reprimand" , "Field event" , "Lofty leap as drastic punishment" , "bar activity?" , "punishing?" .)