Battle soldiers following security into hospital department (10)
I believe the answer is:
engagement
'battle' is the definition.
(synonyms)
'soldiers following security into hospital department' is the wordplay.
'soldiers following' becomes 'enm' (I am not sure about this - if you are sure you should believe this answer much more).
'security' becomes 'gage' (I've seen this in another clue).
'into' means one lot of letters goes inside another.
'hospital department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'enm' going around 'gage' is 'engagem'.
'engagem'+'ent'='ENGAGEMENT'
Can you help me to learn more?
(Other definitions for engagement that I've seen before include "calls for signs of commitment" , "publicized by a band" , "Agreement to marry" , "fighting" , "Date, battle, or betrothal" .)