Taunt soldier, born next to base (4)
I believe the answer is:
gibe
'taunt' is the definition.
(I know that gibe is a more specific form of the action taunt)
'soldier born next to base' is the wordplay.
'soldier' becomes 'gi' (GI can mean a US soldier).
'born' becomes 'b' (common abbreviation).
'next to' says to put letters next to each other.
'base' becomes 'e' (Euler's number - base of natural logarithms).
'gi'+'b'+'e'='GIBE'
(Other definitions for gibe that I've seen before include "Hurtful remark" , "Jeer, barb" , "Scoff (at) - taunt" , "Barb, dig" , "A jeering remark" .)