Deal with an unexpected pleasure (5)
I believe the answer is:
treat
I believe this clue is a double definition.
'deal with' is the first definition.
(synonyms)
'an unexpected pleasure' is the second definition.
(I've seen this in another clue)
(Other definitions for treat that I've seen before include "Alternative to trick" , "Pay for someone's food or drink or look after them medically" , "Apply remedies" , "Handle; dainty" , "Joy" .)