Amazing score Tchaikovsky's beginning — it may take your breath away! (6)
I believe the answer is:
corset
'it may take your breath away' is the definition.
(if too tight)
'amazing score tchaikovsky's beginning' is the wordplay.
'amazing' indicates an anagram.
'beginning' indicates taking the first letters.
The initial letter of 'tchaikovsky' is 't'.
'score' anagrammed gives 'corse'.
'corse'+'t'='CORSET'
(Other definitions for corset that I've seen before include "Stays" , "Tight undergarment" , "Tight-fitting ladies' garment" , "Tight bodice" , "Type of bodice" .)