Tiger released in very old film thriller (7)
I believe the answer is:
vertigo
'film thriller' is the definition.
(Hitchcock thriller)
'tiger released in very old' is the wordplay.
'released' indicates anagramming the letters (letters released from their original order).
'in' is an insertion indicator.
'very' becomes 'v' (abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'tiger' is an anagram of 'ertig'.
'v'+'o'='vo'
'ertig' put inside 'vo' is 'VERTIGO'.
(Other definitions for vertigo that I've seen before include "Dizziness due to disorder in sense of balance" , "Sensitivity to heights" , "Problem brought on by heights" , "Trouble with heights" , "source of imbalance" .)