Run a youngster out of Central America (4)
I believe the answer is:
trot
'run' is the definition.
(trot is a kind of run)
'a youngster out of central america' is the wordplay.
'a youngster' becomes 'tot' (tot is a kind of youngster**).
'out of' means one lot of letters goes inside another.
'central' means to look at the middle letters.
The central letter of 'america' is 'r'.
'tot' enclosing 'r' is 'TROT'.
(Other definitions for trot that I've seen before include "Clip (horse)" , "Gait between a walk and a canter" , "leftie" , "Move quite fast" , "Moderate running pace" .)