Beat from start to finish of Beethoven's first (5)
I believe the answer is:
throb
'beat' is the definition.
(throb is a kind of beat)
'from start to finish of beethoven's first' is the wordplay.
'from start to finish' becomes 'thr' (I can't justify this - if you can you should give a lot more credence to this answer).
'of' becomes 'o''.
'beethoven's first' becomes 'b' (tst letter of 'beethoven').
'thr'+'o'+'b'='THROB'
Can you help me to learn more?
(Other definitions for throb that I've seen before include "Pulsate; regular beat" , "Beat quickly from excitement etc" , "Sound of engines" , "One's heart may do it" , "Strong rhythmic beat" .)