A strong drink imbibed by Everyman, twice: fancy that! (7)
I believe the answer is:
imagine
'fancy that' is the definition.
(interjections!)
'a strong drink imbibed by everyman twice' is the wordplay.
'a strong drink' becomes 'gin' (gin is a kind of strong drink).
'imbibed by' indicates putting letters inside.
'everyman' becomes 'i' (where 'Everyman' is the setter of the crossword).
'twice' becomes 'mae' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'i'+'mae'='imae'
'gin' put within 'imae' is 'IMAGINE'.
Can you help me to learn more?
(Other definitions for imagine that I've seen before include "Form a mental image in the mind" , "Picture in mind, envisage" , "Picture to oneself" , "Fancy - dream" , "Believe to be so, suppose" .)