Poses when taking smack on vacation (4)
I believe the answer is:
asks
'poses' is the definition.
(as in posing or asking a question)
'when taking smack on vacation' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'taking' indicates putting letters inside.
'on vacation' means to remove the middle letters (after the inside letters have vacated the word).
'smack' with its centre taken out is 'sk'.
'as' placed around 'sk' is 'ASKS'.
(Other definitions for asks that I've seen before include "Demands (something of someone)" , "Inquiries" , "Makes an inquiry" , "Puts a query" , "Requests information about" .)