Unique - like a close guess? (3-3)
I believe the answer is:
one-off
'unique' is the definition.
(I've seen this before)
'a close guess?' is the wordplay.
'a' becomes 'one'.
'close guess?' becomes 'off' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'one'+'off'='ONE-OFF'
'like' acts as a link.
Can you help me to learn more?
(Other definitions for one-off that I've seen before include "Unique specimen" , "Not repeated, being a single event or object" , "Unrepeatable experience" , "Made or done as a single thing, not repeated" , "Happening only once" .)