Costume head of tennis used to secure success? (7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

Tennis (head of Tennis) WIN SET (to secure success – in tennis);  I think the idea here is  that you ‘use’ the first letter of the word tennis to secure success – at tennis! Is this an Ouroboros clue, where the clue is turning in on itself, trying to eat itself? A twinset is a matching cardigan and jumper for women. It’s practically impossible for Brits of a certain age to hear this word without adding ‘and pearls’. If a psychologist were to do a word association test for oldies, they would be pretty dumb if they used ‘twinset’. Unless, of course, they wanted to identify that sub-set who wanted to be different; the matricides, perhaps?