See irregular verbs in Old English (7)
I believe the answer is:
observe
'see' is the definition.
(thesaurus)
'irregular verbs in old english' is the wordplay.
'irregular' is an anagram indicator.
'in' is an insertion indicator.
'old english' becomes 'oe' (**).
'verbs' is an anagram of 'bserv'.
'bserv' placed within 'oe' is 'OBSERVE'.
(Other definitions for observe that I've seen before include "Scrutinise or comply with" , "Keep an eye on" , "Watch carefully" , "Verbose (anag.)" , "Watch, take note of" .)