Boiling last egg in order to be helpful (8)
I believe the answer is:
obliging
'be helpful' is the definition.
(I've seen this before)
'boiling last egg in order' is the wordplay.
'last' suggests the final letters.
'in order' indicates anagramming the letters (the letters in a new order).
The final letter of 'egg' is 'g'.
'boiling'+'g'='boilingg'
'boilingg' with letters rearranged gives 'OBLIGING'.
'to' acts as a link.
(Other definitions for obliging that I've seen before include "binding" , "Agreeable" , "Courteous and helpful, willing to do a favour" , "Cheerfully willing to do favours" , "Compelling" .)