No - Don't look glum! Getting the correct answer is 90% of the task and sorting out the whole wordplay is only 10%.
I saw your solution and wondered how the Rocks fitted in! Then I realised that the clue was sharper than I first thought. By my posting I wanted to add to your answer not take anything away!
Thanks for coming back, crofter. I'm not cross with you, just cross with myself. The terrible truth is that one reaches a plateau in ones ability to do crosswords - and then one starts to go down. I do, anyway. Depressing!