Creature nowadays having a red back (5)
I believe the answer is:
adder
'creature' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'nowadays having a red back' is the wordplay.
'nowadays' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'having' says to put letters next to each other.
'back' is a reversal indicator.
'red' in reverse letter order is 'der'.
'ad'+'der'='ADDER'
Can you help me to learn more?
(Other definitions for adder that I've seen before include "One contributing more" , "Britain's only venomous snake" , "Viper common in northern Eurasia" , "poisoner" , "calculator?" .)