If that man enters outskirts of Wainfleet, that woman's following (7)
I believe the answer is:
whether
'if' is the definition.
(I've seen this before)
'man enters outskirts of wainfleet that woman's following' is the wordplay.
'man' becomes 'he' (**).
'enters' is an insertion indicator.
'outskirts of' suggests removing the centre.
'that woman's' becomes 'her' (I've seen this before).
'following' means one lot of letters go next to another.
'wainfleet' with its middle removed is 'wt'.
'he' placed into 'wt' is 'whet'.
'whet'+'her'='WHETHER'
'that' is the link.
(Other definitions for whether that I've seen before include "Word introduces alternative" , "Expression of doubt" , "-- or no means in any event" , "Conjunction indicating choice" , "If in fact" .)