See's ever so worried about Bishop (7)
I believe the answer is:
observe
'see's' is the definition.
(thesaurus)
'ever so worried about bishop' is the wordplay.
'worried' indicates anagramming the letters.
'about' is an insertion indicator.
'bishop' becomes 'b' (abbreviation used in chess).
'ever'+'so'='everso'
'everso' is an anagram of 'oserve'.
'oserve' going around 'b' is 'OBSERVE'.
(Other definitions for observe that I've seen before include "Keep; notice" , "Obverse (anag.)" , "Watch attentively" , "Espy" , "Notice; study" .)