Last bit of pine inserted into the joist later (10)
I believe the answer is:
thereafter
'later' is the definition.
(I've seen this before)
'last bit of pine inserted into the joist' is the wordplay.
'last bit of' suggests the final letters.
'inserted into' is an insertion indicator.
'joist' becomes 'rafter' (I can't justify this - if you can you should believe this answer much more).
The final letter of 'pine' is 'e'.
'the'+'rafter'='therafter'
'e' inserted within 'therafter' is 'THEREAFTER'.
Can you help me to learn more?
(Other definitions for thereafter that I've seen before include "Next" , "Subsequently" , "Following that time" , "later" .)