English international lacks energy to run, for the main part (5,5)
I believe the answer is:
lions share
'the main part' is the definition.
(I've seen this before)
'english international lacks energy to run' is the wordplay.
I cannot really see how this works, but
'english' could be 'e' (abbreviation) and 'e' is located in the answer.
'international' could be 'lion' (international rugby player for Britain) and 'lion' is present in the answer.
'run' could be 'r' (cricket abbreviation) and 'r' is located in the answer.
This explanation may well be incorrect...
'for' acts as a link.
Can you help me to learn more?
(Other definitions for lions share that I've seen before include "For the greater part" , "Largest portion" , "Main part" , "Largest part" , "Principal part" .)