Student's jog spoiled by morning congestion (6)
I believe the answer is:
logjam
'congestion' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'student's jog spoiled by morning' is the wordplay.
'student' becomes 'L' (as in L-plates for learner drivers).
'spoiled' indicates an anagram.
'by' means one lot of letters go next to another.
'morning' becomes 'am' (as in 12:00 AM).
'jog' with letters rearranged gives 'ogj'.
'l'+'ogj'+'am'='LOGJAM'
Can you help me to learn more?
(Other definitions for logjam that I've seen before include "blockage" , "deadlock" , "bottleneck" , "Major stoppage" , "impasse" .)