Quite serious (5)
I believe the answer is:
sober
(Other definitions for sober that I've seen before include "Judge said to be so" , "Sedate - staid" , "not moved" , "Teetotal" , "Dignified and sombre in manner or character" .)
I believe the answer is:
sober
(Other definitions for sober that I've seen before include "Judge said to be so" , "Sedate - staid" , "not moved" , "Teetotal" , "Dignified and sombre in manner or character" .)