Starting point for Swiss city lacking top wine (4)
'starting point' is the definition.
(I've seen this before)
'swiss city lacking top wine' is the wordplay.
'swiss city' becomes 'basel' (I've seen this before).
'lacking top' means to remove the first letter.
'wine' with its initial letter taken away is 'ine'.
'basel'+'ine'='BASELINE'
'for' acts as a link.
(Other definitions for baseline that I've seen before include "Out beyond this" , "Marks limit of play on tennis court" , "yardstick" , "Back of tennis court - standard" , "Starting point" .)
'starting point' is the definition.
(thesaurus)
I don't understand the rest of the clue.
(Other definitions for base that I've seen before include "floor" , "centre from which soldiers operate" , "Ignoble - HQ" , "Not a noble" , "home?" .)