Seeking the best conclusion, possibly in fear (5)
I believe the answer is:
after
'seeking' is the definition.
(I've seen this in another clue)
'the best conclusion possibly in fear' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'best' could be 'a' and 'a' is located in the answer.
The remaining letters 'fer' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for after that I've seen before include "In honour of" , "Subsequent to" , "Pursuing" , "Behind; in quest of" , "Looking for" .)