What might make guy fast?
I believe the answer is:
tent peg
'what might' is the definition.
I can't tell whether this definition defines the answer.
'guy fast?' is the wordplay.
'guy' becomes 'tent' (I've seen this before).
'fast?' becomes 'peg' (I can't explain this - if you can you should give a lot more credence to this answer).
'tent'+'peg'='TENT-PEG'
'make' acts as a link.
Can you help me to learn more?
(Other definitions for tent peg that I've seen before include "Camping equipment" , "Canvas fastener" , "What guy is steadied by" , "It's driven into the ground to support portable shelter" , "Fixer for guy" .)