Goat god one about to cause fear (5)
I believe the answer is:
panic
'fear' is the definition.
(panic is a kind of fear)
'goat god one about' is the wordplay.
'goat god' becomes 'pan' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'about' becomes 'c' (abbreviation for 'circa').
'pan'+'i'+'c'='PANIC'
'to cause' is the link.
(Other definitions for panic that I've seen before include "Alarm, scare" , "Frantic fright" , "Mass fear" , "Go to pieces" , "much unease" .)