Pine tree finally included in story (5)
I believe the answer is:
yearn
'pine' is the definition.
('yearn' can be a synonym of 'pine')
'tree finally included in story' is the wordplay.
'finally' indicates one should take the final letters.
'included in' is an insertion indicator.
'story' becomes 'yarn' ('yarn' can be a synonym of 'story').
The final letter of 'tree' is 'e'.
'e' put within 'yarn' is 'YEARN'.
(Other definitions for yearn that I've seen before include "Long (for something)" , "Mark of injury" , "Have a great longing" , "Desire, want" , "Curdle" .)