Adjust to new conditions (5)
'adjust to new conditions' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for adapt that I've seen before include "Tailor" , "match" , "Make suitable for new purpose" , "Adjust (to changes)" , "Accommodate" .)
(Other definitions for readapt that I've seen before include "again demonstrate versatility" , "make further modifications" , "undergo further change" , "Again adjust to changed conditions" , "Once again modify" .)