Balanced knife on head of louche earl (6)
I believe the answer is:
stable
'balanced' is the definition.
(similar in meaning)
'knife on head of louche earl' is the wordplay.
'knife' becomes 'stab' (synonyms).
'on' is a charade indicator (letters next to each other).
'head of' suggests taking the first letters.
The first letters of 'louche earl' is 'le'.
'stab'+'le'='STABLE'
(Other definitions for stable that I've seen before include "Equine housing" , "Durable; horse shed" , "Steadfast, resolute" , "Home for horses" , "Not likely to change" .)