Paid early? There's a thought in that! (4)
I believe the answer is:
idea
'a thought in that' is the definition.
'idea' can be an answer for 'a thought' ('idea' can be a synonym of 'thought'). I'm not certain of the rest of the definition.
'paid early?' is the wordplay.
'IDEA' is hidden within the letters.
However, I am not sure how this is indicated.
'there's' is the link.
Can you help me to learn more?
(Other definitions for idea that I've seen before include "Notion, image" , "A suspicion of" , "Flash of inspiration?" , "intellectual product" , "Thought, conception" .)