Deem a sober type (5)
I believe the answer is:
judge
'deem' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for judge that I've seen before include "Form an opinion of" , "Senior officer of the law" , "Arbitrate" , "rule" , "Arbitrator" .)