Some fear a mad animal if it's fast (7)
I believe the answer is:
ramadan
'it's fast' is the definition.
(month of fasting in Islam)
'some fear a mad animal' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'RAMADAN' is hidden within 'fear a mad animal'.
'if' is the link.
(Other definitions for ramadan that I've seen before include "Muslim period of fasting" , "Muslims observe this" , "Islam's holiest month" , "Islam holy month" , "Muslim month of fasting from sunrise to sunset" .)