I'm assuming you want 120mm fans as I think all Antec CLCs use 120mm fans. If you are only going to replace one fan and CLC has more than 1 fan it would be advisable to either replace all fans with same model or replace the bad one with same model as other fans being used.
Fans Grandmaster Fap! suggested are both good. PH-F120MP specs are 53.3cfm, 1.72mm H2O & 1800rpm and Arctic P12 are 56cfm, 2.2mm H2O & 1800rpm so similar with Arctic P12 being a little better as well as lower priced. I have used PH-F120MP and found them to be very nice fans. I have not used Arctic P12 but others that have like them a lot. I have used Arctic F series 90mm and 120mm and found them to quite good, especially considering their low price. They are almost as good as fans costing 3-5 times more money.
PH-F120MP in 2-packs are £14.99 (£7.50 each) and 3-packs are £26.00 (£8.67 each).
https://www.overclockers.co.uk/two-...120mm-fan-radiator-performance-bu-002-pt.html
https://www.overclockers.co.uk/thre...120mm-fan-radiator-performance-bu-001-pt.html
Arctic P12 is £5.99.
Arctic P12 PWM PST is £5.95. PST has female fan connector so fans can be daisy-chained together instead of each needing a fan header.