Nice surprise in Portreath (5)
I believe the answer is:
treat
'nice surprise' is the definition.
(I've seen this before)
'in portreath' is the wordplay.
'in' indicates the answer is hidden within the clue.
'TREAT' is hidden in the letters of 'portreath'.
(Other definitions for treat that I've seen before include "Apply remedies" , "Entertain at one's own expense" , "Negotiate to reach an agreement" , "Engage in negotiations" , "Pay for someone's food or entertainment" .)