Indication of what's hot or cold may be here, readily available (2,3)
I believe the answer is:
on tap
This could be a double definition.
'indication of what's hot or cold may be here' is the first definition.
The definition suggests a singular noun but the answer is not. However, I know that both 'hot' and 'cold' relate to this answer.
'readily available' is the second definition.
(I've seen this before)
(Other definitions for on tap that I've seen before include "Always available" , "readily accessible" , "Ready to be drawn off, say beer" , "Where you may see H or C" , "Ready for immediate use" .)