Divide by two (well divided by five) (5)
I believe the answer is:
halve
'divide by two' is the definition.
(synonyms)
'well divided by five' is the wordplay.
'well' becomes 'hale' (I've seen this in another clue).
'divided by' means one lot of letters goes inside another.
'five' becomes 'V' (Roman numeral).
'hale' enclosing 'v' is 'HALVE'.
(Other definitions for halve that I've seen before include "Share equally" , "Divide fifty-fifty" , "Bisect" , "Cut down substantially" , "Divide into two equal pieces" .)