Losing water to make ice first, it's a way of preservation (6-6)
I believe the answer is:
freeze-drying
'losing water to' is the definition.
I can't tell whether this definition defines the answer.
'ice first it's a way of preservation' is the wordplay.
'ice' becomes 'freeze' (I've seen this before).
'first' means one lot of letters go next to another.
'it's a way of preservation' becomes 'drying' (I can't explain this - if you can you should give a lot more credence to this answer).
'freeze'+'drying'='FREEZE-DRYING'
'make' is the link.
Can you help me to learn more?
(Other definitions for freeze-drying that I've seen before include "Rapid vacuum cooling for storage" , "Vacuum preservation technique" .)