Scared by blunder provided, held by United (9)
I believe the answer is:
terrified
'scared' is the definition.
(terrifying is a kind of scaring)
'blunder provided held by united' is the wordplay.
'blunder' becomes 'err' (I've seen this before).
'provided' becomes 'if'.
'held by' indicates putting letters inside.
'united' becomes 'tied' ('tied' can be similar in meaning to 'united'**).
'err'+'if'='errif'
'errif' put within 'tied' is 'TERRIFIED'.
'by' acts as a link.
(Other definitions for terrified that I've seen before include "Panic-stricken - dire refit (anag)" , "Scared stiff" , "Greatly frightened" , "Extremely frightened" .)