High-speed hand-walking contest is a very dangerous competition (4,4)
I believe the answer is:
arms race
'competition' is the definition.
(arms race is a kind of competition)
'high-speed hand-walking contest is a very dangerous' is the wordplay.
I cannot quite understand how this works, but
'speed' could be 'race' (synonyms) and 'race' is found in the answer.
'hand' could be 'r' (abbreviation for right, as in the right-hand side) and 'r' is found in the answer.
'a' is present in the answer.
The remaining letters 'ms' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for arms race that I've seen before include "rush to war" , "Weaponry competition" , "military competition" , "Weapon competition" , "A hostile international competition" .)