Stuck on half of one - just cannot suss it out! 18d Of conditions in which cloud ceiling and horizontal visibility are nothing. (4-4) I have ZERO-??R?. IF the answer to 26a is DOZIER then I suppose...
4 down (9) P_R_T_IO_N Insecticide containing phosphorus and sulphur.
20 across (4) I__H Scottish and Irish word for a low-lying meadow.
25 across (6) _F_H_M West Sussex village north of Arundel....