He has a terrible dread about getting stuck (7)
I believe the answer is:
adhered
'stuck' is the definition.
('adhere' can be a synonym of 'stick')
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for adhered that I've seen before include "Stuck to, remained loyal" , "Stuck - redhead (anag)" , "Stuck; glued" , "Stuck (to something)" , "Showed sticking power" .)