A source of light -- and forces panicked outside (8)
I believe the answer is:
alfresco
'outside' is the definition.
(synonyms)
'a source of light and forces panicked' is the wordplay.
'source of' says to take the initial letters (the start - or source - of the word).
'and' is a charade indicator (letters next to each other).
'panicked' indicates anagramming the letters.
The initial letter of 'light' is 'l'.
'forces' anagrammed gives 'fresco'.
'a'+'l'+'fresco'='ALFRESCO'
(Other definitions for alfresco that I've seen before include "where it's cool" , "Outside" , "In the open air" , "Meal eaten in the outdoors" , "Out of doors" .)