Relative in Dalwhinnie celebrating (5)
I believe the answer is:
niece
'relative' is the definition.
(type of relative)
'in dalwhinnie celebrating' is the wordplay.
'in' says the answer is hidden in the clue.
'NIECE' is hidden in the letters of 'dalwhinnie celebrating'.
(Other definitions for niece that I've seen before include "Brother's daughter" , "member of different generation" , "Preparation for curdling milk" , "Family relation" , "A sibling's child" .)