At beginning constable attending a search in underground area (8)
I believe the answer is:
catacomb
'underground area' is the definition.
(a catacomb is an underground tomb)
'at beginning constable attending a search' is the wordplay.
'at' means one lot of letters go next to another.
'beginning' says to take the initial letters.
'attending' becomes 'at' (e.g. at school means attending school).
'search' becomes 'comb' (combing is a kind of searching).
The first letter of 'constable' is 'c'.
'c'+'at' is 'cat'.
'cat'+'a'+'comb'='CATACOMB'
'in' is the link.
(Other definitions for catacomb that I've seen before include "burial site" , "Burial chamber with vaulted tunnels" , "crypt" , "Subterranean cemetery" , "tunnel for burial" .)