If you play cleave before move to battlefield cN opponent gust the unit

Misinterpretation of the question. Question states Cleave before move.

If the unit is Might 3 or less and at a Battlefield (going to gank to the other Battlefield with the move) than yes. Playing cleave creates a chain to which a reaction (like Gust) can be played. If the target unit has 3 might or less it is a legal target for Gust. Gust will sit on top of Cleave in the chain and will resolve first. The unit will be returned to hand and Cleave will mistarget during resolution. If the unit is in base, then no as Gust is restricted to targeting units at Battlefields. And the moment you move to a Battlefield with opposing units you will be designated as attacker and Assault will increase your might before any reaction window opens for Gust to be played. UNLESS your unit has a 'when I move' trigger. Then, similar to the example above, a chain will be created to which reactions can be played. And your unit will be at a Battlefield but a Combat Showdown will not have been staged yet (rule 321) as there is an existing chain from the 'when I move' triggered ability.