Way proficiency produces steadiness (9)
I believe the answer is:
stability
'steadiness' is the definition.
(stability is a kind of steadiness)
'way proficiency' is the wordplay.
'way' becomes 'st'.
'proficiency' becomes 'ability' (I've seen this before).
'st'+'ability'='STABILITY'
'produces' is the link.
(Other definitions for stability that I've seen before include "Balanced, settled state" , "not displayed by Humpty-Dumpty" , "Balance" , "Steadiness; fixity" , "State of steadiness and reliability" .)