Answer: deepening

AnswerCrossword Clue
DEEPENINGChanging the channel?
DEEPENINGDredging a river or harbor channel.
DEEPENINGBecoming abstruse
deepeningMake or become deep or deeper
deepeningDEEPEN, to make deep (extending far down from the surface)
deepening(of a weather system) Decrease in barometric pressure