One always behind Labour lass on the rise (7)
I believe the answer is:
laggard
'one' is the definition.
Both the answer and definition are adjectives. Maybe there's a link between them I don't understand?
'always behind labour lass on the rise' is the wordplay.
'always behind labour' becomes 'drag' (I can't explain this - if you can you should give a lot more credence to this answer).
'lass' becomes 'gal' (both can mean a girl).
'on the rise' is a reversal indicator (in a down clue, letters go up).
'drag'+'gal'='draggal'
'draggal' written backwards gives 'LAGGARD'.
Can you help me to learn more?
(Other definitions for laggard that I've seen before include "slowcoach" , "One failing to keep up" , "Moving slowly" , "He drags along behind" , "one going slowly" .)