Not seen but heard in light fog? (6)
I believe the answer is:
missed
'not seen' is the definition.
The answer and definition can be both related to thinking as well as being past participle verbs.
Perhaps there's a link between them I don't understand?
'heard in light fog?' is the wordplay.
'heard in' indicates a 'sounds like' (homophone) clue.
'light fog?' becomes 'mist' (I've seen this in another clue).
'mist' is a homophone of 'MISSED'.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for missed that I've seen before include "failed to see" , "Suffered the lack of" , "came too late" , "Failed to hit target" , "Overlooked ?- ?? but not forgotten!" .)