Celtic priest (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
druid
'celtic priest' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for druid that I've seen before include "Ancient Celt priest" , "Pre-Christian Celtic priest" , "Ancient Celtic priest" , "Ancient priest of Wales" , "An Eisteddfod official" .)