13d) Under stress, it's difficult to circumvent rough seas (8) H?R???E?
14d) Snare takes the tail off the dog (7) ?N???G?
16d) The north shaft is difficult to squeeze through (6) A?R?O?
20d) Wine given to one who is discharged (4) S?C?
2d) Calculations about the first of the petrol and oil reserves (5) ?U?P?
6d) Oscillator needed for one who's lively and up-to-date (7) ?W?N?E?