With command from military, Gaels dispersed (13)
I believe the answer is:
magisterially
'with command' is the definition.
(in a commanding or magisterial way)
'military gaels dispersed' is the wordplay.
'dispersed' indicates anagramming the letters.
'military'+'gaels'='militarygaels'
'militarygaels' is an anagram of 'MAGISTERIALLY'.
'from' is the link.
(Other definitions for magisterially that I've seen before include "Like a dictator" , "in authoritative way" .)