For the cards, they’re real experts (4)
I believe the answer is:
aces
This might be a double definition.
'for the cards' is the first definition.
(ace is a kind of card)
'real experts' is the second definition.
'aces' can be an answer for 'experts' (ace is a kind of expert). I am not certain of the 'real' bit.
'they're' acts as a link.
Can you help me to learn more?
(Other definitions for aces that I've seen before include "They're high and low on cards" , "Top (or bottom) cards" , "Playing cards with single pips on their faces" , "Unreturnable services" , "excellent service" .)