Facts in emergency (3)
I believe the answer is:
gen
'facts' is the definition.
(thesaurus)
'in emergency' is the wordplay.
'in' indicates a hidden word.
'GEN' can be found hidden inside 'emergency'.
(Other definitions for gen that I've seen before include "Information yielded" , "Lowdown (sl.)" , "Info" , "Knowledge" , "opening book, in short" .)