Under pressure, worked shifts say, in potentially dangerous situation (6,3)
I believe the answer is:
powder keg
'potentially dangerous situation' is the definition.
(I've seen this in another clue)
'under pressure worked shifts say' is the wordplay.
'under' says to put letters next to each other (in a down clue, some letters go below others).
'pressure' becomes 'p' (scientific abbreviation).
'shifts' indicates an anagram.
'say' becomes 'eg' (both can mean for example).
'worked' with letters rearranged gives 'owderk'.
'p' next to 'owderk' is 'powderk'.
'powderk'+'eg'='POWDER KEG'
'in' acts as a link.
(Other definitions for powder keg that I've seen before include "Guy Fawkes's kind of barrel?" , "Potential source of explosive violence?" , "Dangerous situation" , "Volatile situation" , "Potentially explosive situation?" .)