Drop in and see the lot (4)
I believe the answer is:
call
'drop in' is the definition.
(thesaurus)
'see the lot' is the wordplay.
'see' becomes 'c' (the word for the letter, according to Chambers).
'the lot' becomes 'all' (I've seen this before**).
'c'+'all'='CALL'
'and' is the link.
(Other definitions for call that I've seen before include "That is enough" , "Ring; name" , "Visit; telephone" , "Cry - summon" , "Entitle" .)