Popular figure out with conservationists on the rocks (9)
I believe the answer is:
insolvent
'on the rocks' is the definition.
(I've seen this before)
'popular figure out with conservationists' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'figure out' becomes 'solve' (synonyms).
'with' means one lot of letters go next to another.
'conservationists' becomes 'NT' (abbreviation for National Trust).
'in'+'solve'+'nt'='INSOLVENT'
(Other definitions for insolvent that I've seen before include "In the red" , "deep in debt?" , "Unable to pay debts owed" , "unable to raise the wind" , "Broke" .)