Risk damage when drilling patent bucket? (9)
I believe the answer is:
overtrain
'risk damage when drilling' is the definition.
(train or drill too hard)
'patent bucket?' is the wordplay.
'patent' becomes 'overt' (both can mean obvious).
'bucket?' becomes 'rain' (eg bucketing down means raining).
'overt'+'rain'='OVERTRAIN'
(Other definitions for overtrain that I've seen before include "Spend too much time on exercises" , "Run past peak, perhaps" , "Prepare too hard" .)