Ostentatiously display fraternal love, initially, in front of relative (6)
I believe the answer is:
flaunt
'ostentatiously display' is the definition.
(I've seen this before)
'fraternal love initially in front of relative' is the wordplay.
'initially' suggests taking the first letters.
'in front of' says to put letters next to each other.
'relative' becomes 'aunt' (aunt is a kind of relative**).
The initial letters of 'fraternal love' is 'fl'.
'fl'+'aunt'='FLAUNT'
(Other definitions for flaunt that I've seen before include "show with pride" , "Display ostentatiously, show-off" , "Display ostentatioulsy, brandish" , "wave" , "Display ostentatiously or boastfully" .)