Popular park is kept aside (2,7)
I believe the answer is:
in reserve
'aside' is the definition.
(synonyms)
'popular park is kept' is the wordplay.
I cannot quite see how this works, but
'popular' could be 'in' ('in' can mean trendy) and 'in' is present in the answer.
The remaining letters 'reserve' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for in reserve that I've seen before include "Held back" , "Set aside" , "available for use if needed" , "extra" , "Kept back" .)