Almost all inside; great in the end (6)
I believe the answer is:
finale
'the end' is the definition.
(I've seen this before)
'almost all inside great' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'inside' is an insertion indicator.
'great' becomes 'fine' (I can't explain this - if you can you should give a lot more credence to this answer).
'all' with its final letter removed is 'al'.
'al' inserted within 'fine' is 'FINALE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for finale that I've seen before include "Last song etc" , "Last item of event" , "Conclusion of a performance" , "Last part of something" , "Conclusion of a piece of music" .)