Expressing gratitude over advanced ability (6)
I believe the answer is:
talent
'ability' is the definition.
(a talent is an ability)
'expressing gratitude over advanced' is the wordplay.
I cannot quite see how this works, but
'gratitude' could be 'ta' (I've seen this in other clues) and 'ta' is present in the answer.
'advanced' could be 'lent' (advance can mean to lend) and 'lent' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for talent that I've seen before include "Natural aptitude of an old coin" , "Natural aptitude or skill" , "Innate skill" , "Natural skill or flair" , "Attractive people" .)