Sudden inspiration? (4)
I believe the answer is:
gasp
'sudden inspiration?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gasp that I've seen before include "Convulsive breath" , "First Greek letter" , "Have trouble breathing" , "Inhale sharply with astonishment" , "Sudden intake of breath" .)