Violin piece by leader strengthened position (10)
I believe the answer is:
bridgehead
'strengthened position' is the definition.
'bridgehead' can be an answer for 'position' (bridgehead is a kind of position). I am unsure of the 'strengthened' bit.
'violin piece by leader' is the wordplay.
'violin piece' becomes 'bridge'.
'by' is a charade indicator (letters next to each other).
'leader' becomes 'head' (head is a kind of leader).
'bridge'+'head'='BRIDGEHEAD'
Can you help me to learn more?
(Other definitions for bridgehead that I've seen before include "Advantageous position" , "defensive position" , "Secured position from which to advance" , "Strong position secured inside enemy territory" , "Advanced position secured in enemy territory" .)