Fear of finishing last by mistake (6)
I believe the answer is:
terror
'fear of finishing' is the definition.
'terror' can be an answer for 'fear' (terror is a kind of fear). I am not certain of the 'of finishing' bit.
'last by mistake' is the wordplay.
'last' becomes 't' (I've seen this in other clues).
'by' is a charade indicator (letters next to each other).
'mistake' becomes 'error' (synonyms).
't'+'error'='TERROR'
Can you help me to learn more?
(Other definitions for terror that I've seen before include "Sheer fright" , "Fear - mischievous child" , "Extreme fright or dread" , "Ovewhelming fear" , "Organised political violence" .)