Tenor worried about a song's introduction — it might be high! (7)
I believe the answer is:
treason
'it might be high' is the definition.
(as in high treason)
'tenor worried about a song's introduction' is the wordplay.
'worried' indicates an anagram (worry can mean to interfere with or disturb).
'about' indicates putting letters inside.
'introduction' says to take the initial letters.
The first letter of 'songs' is 's'.
'tenor' with letters rearranged gives 'treon'.
'a'+'s'='as'
'treon' placed around 'as' is 'TREASON'.
(Other definitions for treason that I've seen before include "Crime of treachery against the state" , "Crime of national betrayal" , "Betrayal of one's nation" , "One's art? (anag)" , "Mutiny" .)