Top area seen by camper regularly (4)
I believe the answer is:
acme
'top' is the definition.
(synonyms)
'area seen by camper regularly' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'seen by' is a charade indicator (letters next to each other).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'camper' are 'cme'.
'a'+'cme'='ACME'
(Other definitions for acme that I've seen before include "Point of maximum development" , "highest position" , "Summit, crowning point" , "Height of achievement" , "Highest level or degree attainable" .)