Boost position entering sports competition (5,2)
I believe the answer is:
crank up
'boost' is the definition.
(both can mean to lift up)
'position entering sports competition' is the wordplay.
'position' becomes 'rank' (rank is a kind of position).
'entering' means one lot of letters goes inside another.
'sports competition' becomes 'cup' (eg the FA Cup).
'rank' placed inside 'cup' is 'CRANK UP'.
(Other definitions for crank up that I've seen before include "Increase" , "Strengthen" .)