Solution:LOST, TALK, WALK, KALM, SHAW
As per the instruction,
Arranging in the reverse order,
TSOL , KLAT , KLAW , MLAK , WAHS
After arranging in the words as per english dictionary,
KLAT , KLAW , MLAK , TSOL , WAHS
Now, middle word = MLAK, which is written as KALM