Dutch regularly chases women, at first ignoring size (5)
I believe the answer is:
width
'size' is the definition.
(thesaurus)
'dutch regularly chases women at first ignoring' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'chases' is a charade indicator (letters next to each other).
'women' becomes 'w'.
'at first' says to take the initial letters.
The initial letter of 'ignoring' is 'i'.
The alternate letters of 'dutch' are 'dth'.
'w'+'i'='wi'
'dth' after 'wi' is 'WIDTH'.
(Other definitions for width that I've seen before include "Distance from side to side" , "Lateral extent" , "compass" , "Broadness" , "Lateral dimension" .)