Crossword Genius

Strengthen lead in tennis, having an advantage (4,2)

Ross

I believe the answer is:

tone up

'strengthen' is the definition.
(I know that strengthen can be written as tone up)

'lead in tennis having an advantage' is the wordplay.
'lead in' indicates taking the first letters.
'having an advantage' becomes 'one up' (having one more point than an opponent).
The first letter of 'tennis' is 't'.
't'+'oneup'='TONE-UP'

(Another definition for tone up that I've seen is " Make healthier".)

I've seen this clue in The Times.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.