Fearfully rigid? (6,5)
I believe the answer is:
scared stiff
'fearfully rigid?' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'fearfully rigid?' is the wordplay.
'fearfully' becomes 'scared' (I can't justify this - if you can you should give a lot more credence to this answer).
'rigid?' becomes 'stiff' (synonyms).
'scared'+'stiff'='SCARED STIFF'
Can you help me to learn more?
(Other definitions for scared stiff that I've seen before include "Petrified" , "Frightened to death!" .)