Warned a religious man, having solved his omen (10)
I believe the answer is:
admonished
'warned' is the definition.
('admonish' can be a synonym of 'warn')
'a religious man having solved his omen' is the wordplay.
'religious man' becomes 'DD' (abbreviation for Doctor of Divinity degree).
'having' means one lot of letters goes inside another.
'solved' is an anagram indicator (the anagram must be solved).
'his'+'omen'='hisomen'
'hisomen' with letters rearranged gives 'monishe'.
'dd' enclosing 'monishe' is 'dmonished'.
'a'+'dmonished'='ADMONISHED'
(Other definitions for admonished that I've seen before include "Reproved" , "Told off" , "Rebuked" , "given slap on the wrist?" .)