it's hard to tell if it's really wrist flexibility or shoulder flexibility without seeing. If i was to venture a guess, i'd say shoulder since you bench a lot. My shoulders are flexible enough to hold a front squat and clean, but if my elbows are low, they're not enough.
Plus, if you can hold the bar now, and your elbows aren't high enough, i'd venture that it's not wrists, but i could be wrong.
Are you able to rack a front squat w/ a clean grip?
check this out. Specifically what Danny and i said..
Front Squats and wrist flexibility