not your long suit

not (one's) long suit

Not something one is particularly good or adept at. I'd avoid going for humor in your speech—jokes aren't really your long suit. Social etiquette has never been my long suit.
See also: long, not, suit

not your long suit

If something is not your long suit, you are not good at it. Note: The following expressions refer to the four suits in a pack of cards: diamonds, hearts, clubs, and spades. Tact has never been my long suit. Charm was never Michael's long suit. Note: If a large number of a player's cards belong to a particular suit, you can call that suit their long suit.
See also: long, not, suit