I did something like this before but I think this one is better executed. This... isn't all that easy but it should come like a blinding flash from the blue.
First nudges: The grid is an odd size
Other then the first clue there aren't really any direct hints
So if you imagine the B's as being kind of bumpy does the grid look like anything or remind you of anything
There's some hints that mention that other letters such as TDNA don't count.
B is the only letter that matters
The clue about OTHER being a headless (B)OTHER means that although the B's are bumpy every thing else is smooth and no other letters matter.
Doesn't the grid remind you of anything?
Maybe you found a six letter word
But the prompt says the answer is a letter, not a word
Does the word look like anything?
What about all those references to seeing things in the clues?
BX ... XX
XX ... BB
BX ... BX
XX ... XX
BX ... XB
BX ... XX
BB
LE
BB
XX