Pin-up or pin down? (4)
I believe the answer is:
stud
'pin' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for stud that I've seen before include "Part of a football boot" , "A horse breeding farm" , "Stallion for breeding - fastener" , "Style of poker" , "Horse-breeding farm" .)