Make certain working nurse has English (6)
I believe the answer is:
ensure
'make certain' is the definition.
('ensure' can be a synonym of 'make certain')
'working nurse has english' is the wordplay.
'working' indicates an anagram.
'has' is an insertion indicator.
'english' becomes 'e' (abbreviation**).
'nurse' anagrammed gives 'nsure'.
'nsure' placed around 'e' is 'ENSURE'.
(Other definitions for ensure that I've seen before include "See run (anag)" , "Make certain or safe" , "Make certain (something will occur)" , "Make certain, secure" , "Make certain, confirm" .)