Free, in a way, but it comes at a cost (6)
I believe the answer is:
ransom
'a cost' is the definition.
(ransom is a kind of cost)
'free in a way but it comes' is the wordplay.
I cannot quite see how this works, but
'a' could be 'an' and 'an' is located in the answer.
'way' could be 's' (Compass direction - South) and 's' is present in the answer.
The remaining letters 'rom' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'at' acts as a link.
Can you help me to learn more?
(Other definitions for ransom that I've seen before include "Ready to release prisoner" , "Payment demanded for release of captive" , "Payment for the release of someone" , "money from reluctant donor" , "Buy freedom" .)