Look for the letter a teetotaller's lost! (4)
I believe the answer is:
leer
'look' is the definition.
(I know that leer is a type of look)
'letter a teetotaller's lost' is the wordplay.
'a teetotaller' becomes 'tt' (abbreviation).
'lost' is a deletion indicator.
'letter' with 'tt' taken away is 'LEER'.
'for the' is the link.
(Other definitions for leer that I've seen before include "Lecherous look" , "Look lasciviously at" , "Suggestive or sneering look" , "Lewd look" , "Look suggestively" .)