Lear, mad, terribly worried (7)
I believe the answer is:
alarmed
'worried' is the definition.
(I've seen this before)
'lear mad terribly' is the wordplay.
'terribly' is an anagram indicator.
'lear'+'mad'='learmad'
'learmad' is an anagram of 'ALARMED'.
(Other definitions for alarmed that I've seen before include "Apprehensive" , "Frightened, scared" , "as a door handle may be?" , "Frightened, frightened by danger" , "Experiencing a sudden sense of danger" .)