Heartless man did twist inside, light-headed (5)

I believe the answer is:

giddy

I'm a little stuck... Click here to teach me more about this clue!

'light-headed' is the definition.
(I know that light-headed can be written as giddy)

'heartless man did twist inside' is the wordplay.
'heartless man' becomes 'gy' (I can't justify this - if you can you should believe this answer much more).
'twist' indicates an anagram (a twisted or distorted version of the letters).
'inside' means one lot of letters goes inside another.
'did' anagrammed gives 'idd'.
'gy' placed around 'idd' is 'GIDDY'.

Can you help me to learn more?

(Other definitions for giddy that I've seen before include "Frivolous -- liable to fall" , "Sturdy" , "Flighty or lightheaded." , "Frivolous - in a spin?" , "Dizzy; frivolous" .)

I've seen this clue in The Daily Express.

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.