Being pretentious, striking out at warmth of feeling (9)
I believe the answer is:
affection
'feeling' is the definition.
(I know that affection is a type of affection)
'being pretentious striking out at warmth' is the wordplay.
I cannot really see how this works, but
'at' could be 'on' (location) and 'on' is found in the answer.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for affection that I've seen before include "Goodwill" , "Feeling of fondness" , "Warm regard" , "Fondness or liking" , "Feeling of love or strong liking" .)