Clothing that's a little on the hot side (5)
I believe the answer is:
habit
'clothing' is the definition.
(I know that clothing can be written as habit)
'little on the hot side' is the wordplay.
'little' becomes 'bit' (I've seen this in another clue).
'on' says to put letters next to each other.
'the hot side' becomes 'ha' (I can't explain this - if you can you should give a lot more credence to this answer).
'bit' after 'ha' is 'HABIT'.
'that's a' is the link.
Can you help me to learn more?
(Other definitions for habit that I've seen before include "Monk's robe or repetitive action" , "Settled tendency" , "It's second nature" , "It's worn in order" , "Riding garment" .)