Blow hot and cold, switching? That’s a problem (5)
I believe the answer is:
hitch
'that's a problem' is the definition.
(hitch can mean a problem or delay)
'blow hot and cold switching?' is the wordplay.
'blow' becomes 'hit' (I can't justify this - if you can you should believe this answer much more).
'hot' becomes 'h' (abbreviation, eg on taps).
'and' is a charade indicator (letters next to each other).
'cold' becomes 'C' (eg on taps).
'switching?' says the letters should be written in reverse (switching direction).
'h'+'c'='hc'
'hc' back-to-front is 'ch'.
'hit'+'ch'='HITCH'
Can you help me to learn more?
(Other definitions for hitch that I've seen before include "Snag - free ride" , "Temporary problem" , "Temporary difficulty" , "To travel without paying" , "unite" .)