Exclamation of alarm as a horde assembled (2,4)
I believe the answer is:
oh dear
'exclamation of alarm' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'a horde assembled' is the wordplay.
'assembled' is an anagram indicator.
'a'+'horde'='ahorde'
'ahorde' is an anagram of 'OH DEAR!'.
'as' is the link.
Can you help me to learn more?
(Other definitions for oh dear that I've seen before include "Never mind!" , "I say" , "Cry of dismay" , "That's a shame" , "That's disappointing!" .)