Clue: Make a priest or old monk take one in (6)
Answer: ORDAIN
Explanation: Definition: Make a priest
**OR** + **DA(I)N** ("old monk" *taking* "one" *in*) 
*I'm not sure about Dan – my biblical knowledge lets me down here – but Boatman may be referring to Daniel (as in the book of Daniel, but I thought he was a priest rather than a monk). Edit – Chambers has "dan" as an old word for a cleric)