It is realistic and wise to have this attitude (10)
I believe the answer is:
pragmatism
'this attitude' is the definition.
(I have seen 'Realistic attitude' mean 'pragmatism' so perhaps 'attitude' could also mean 'pragmatism')
'it is realistic and wise' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
'is' is within the answer.
This may be the basis of clue (or it may be nonsense).
'to have' acts as a link.
Can you help me to learn more?
(Other definitions for pragmatism that I've seen before include "Practical approach" , "philosophical approach" , "Realistic attitude" .)