The clues are blooms /growths of what looks like a flower or plant but are wild weeds that grow where not wanted. Some are anagrams.
E.g. Rolling boulders don’t gather on this (4). Answer ... Moss
1. Get the value of a scrap of cloth (7)
2. Nor is this one a squealer (9)
3. Could be a wading with bright legs (8)
7. Corner the market although unwanted (7)
14. Grumps love advanced stealthily (8 & 5)
17. Unwanted one will attach and smother the bloom (8)