Enthusiastic about tagging along without wife (4)
I believe the answer is:
into
'enthusiastic about' is the definition.
(into can mean interested in or enthusiastic about)
'tagging along without wife' is the wordplay.
'tagging along' becomes 'in tow' (I've seen this in another clue).
'without' indicates named letters should be taken away.
'wife' becomes 'w' (abbreviation).
'intow' with 'w' taken away is 'INTO'.
(Other definitions for into that I've seen before include "ignition regularly missing" , "Expression of division" , "To a point within - not I" , "Taking a lively and active interest in (colloq.)" , "Knowledgeable about" .)