It may pick and hold a lock (7)
I believe the answer is:
hairpin
This clue might be a double definition.
'it may pick and hold' is the first definition.
The definition suggests a singular noun which matches the answer.
'a lock' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
I also know that 'lock' relates to this answer.
Can you help me to learn more?
(Other definitions for hairpin that I've seen before include "associated with locks" , "Bit of metal" , "Fastener for tresses" , "Very sharp bend in mountain road" , "grip?" .)