Long story involving 27 (5)
I believe the answer is:
yearn
'long' is the definition.
('yearn' can be a synonym of 'long')
'story involving 27' is the wordplay.
'story' becomes 'yarn' ('yarn' can be a synonym of 'story').
'involving' means one lot of letters goes inside another.
'27' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'yarn' going around 'e' is 'YEARN'.
Can you help me to learn more?
(Other definitions for yearn that I've seen before include "Pant - pine" , "wish" , "Long - pine" , "Have an intense feeling of longing" , "Have a great longing" .)