Visit California before the end of April (4)
I believe the answer is:
call
'visit' is the definition.
(synonyms)
'california before the end of april' is the wordplay.
'california' becomes 'cal' (short for California).
'before' says to put letters next to each other.
'the end of' says to take the final letters.
The last letter of 'april' is 'l'.
'cal'+'l'='CALL'
(Other definitions for call that I've seen before include "Ring or visit" , "Entitle" , "Ring; name" , "Assign a name to" , "Telephone - give a name" .)