Taking this position invites a blow in the face (8)
I believe the answer is:
windward
'taking this position invites a' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'blow in the face' is the wordplay.
'blow' becomes 'wind'.
'in the face' becomes 'ward' (I can't justify this - if you can you should give a lot more credence to this answer).
'wind'+'ward'='WINDWARD'
(Other definitions for windward that I've seen before include "wrong side for the seasick?" , "Some islands" , "Side from which the breeze blows" .)