Put out when end of schedule's unknown due to fog (5)
I believe the answer is:
exude
'put out' is the definition.
(to exude is to emit or put out)
'end of schedule's unknown due to fog' is the wordplay.
'end of' indicates one should take the final letters.
'unknown' becomes 'x' (algebra).
'to fog' indicates an anagram (a confusing or foggy ordering of the letters).
The final letter of 'schedule' is 'e'.
'due' anagrammed gives 'ude'.
'e'+'x'+'ude'='EXUDE'
'when' acts as a link.
(Other definitions for exude that I've seen before include "Ooze out or show freely" , "Slowly give out (smell)" , "Give off, odour or sweat" , "Long-legged wader" , "Discharge by sweating" .)