A truant released large American spider (9)
I believe the answer is:
tarantula
'spider' is the definition.
(I know that tarantula is a type of spider)
'a truant released large american' is the wordplay.
'released' is an anagram indicator (letters released from their original order).
'large' becomes 'L' (eg in clothes sizes).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'a'+'truant'='atruant'
'atruant' anagrammed gives 'tarantu'.
'tarantu'+'l'+'a'='TARANTULA'
(Other definitions for tarantula that I've seen before include "Large venomous spider" , "Crawler" , "hairy creature" , "Breed of spider" , "Leggy creature" .)