A dynamic configuration of crest factor reduction in a licensed assisted access radio system. A processing device comprises a detecting block, a clipping pulse generator, a first storage block, a selecting block, a full clipping block and a simplified clipping block. The detecting block performs a listen-before-talk (LBT) procedure on a plurality of carriers in parallel and generates a trigger signal in response to LBT success on one or more carriers. The clipping pulse generator generates, for the carrier(s) with LBT success, a clipping pulse within a time period from the receipt of the trigger signal to the start of user traffic transmission. The first storage block stores the clipping pulse for use by the full clipping block. The selecting block selects the full clipping block when there is user traffic on the carrier(s) and selects the simplified clipping block when there is no user traffic on the carrier(s).