Animal missing? Blast it! (7)
I believe the answer is:
doggone
'blast it' is the definition.
(both are mild curses)
'animal missing?' is the wordplay.
'animal' becomes 'dog' (I have seen 'Domestic animal ' mean 'dog' so perhaps 'animal' could also mean 'dog').
'missing?' becomes 'gone' (synonyms).
'dog'+'gone'='DOGGONE'
(Other definitions for doggone that I've seen before include "expression used by irritated person" , "Infernal" .)