Nimble soldier gets in drink (5)
I believe the answer is:
agile
'nimble' is the definition.
(agile can mean nimble or athletic)
'soldier gets in drink' is the wordplay.
'soldier' becomes 'GI' (term for US soldier).
'gets in' indicates putting letters inside.
'drink' becomes 'ale' (type of beer).
'gi' inserted within 'ale' is 'AGILE'.
(Other definitions for agile that I've seen before include "Spry - energetic" , "Nimble, spry" , "athletic" , "Nimble on the feet" , "Nimble, fleet" .)