Suit made by girl's BFF (8)
I believe the answer is:
diamonds
'suit' is the definition.
(I've seen this before)
'girl's bff' is the wordplay.
I cannot really see how this works, but
'girl' could be 'di' and 'di' is located in the answer.
This explanation may well be incorrect...
'made by' is the link.
Can you help me to learn more?
(Other definitions for diamonds that I've seen before include "Pieces of crystalline carbon valued as gems" , "Pieces of the hardest known mineral" , "Precious gems" , "where some Americans find sporting action" , "Very hard, very expensive gems" .)