Policemen put outside new iron feather-star (7)
I believe the answer is:
crinoid
'feather-star' is the definition.
I can't judge whether this defines the answer.
'policemen put outside new iron' is the wordplay.
'policemen' becomes 'CID' (abbreviation for Criminal Investigation Department).
'put outside' indicates putting letters inside.
'new' is an anagram indicator.
'iron' is an anagram of 'rino'.
'cid' going around 'rino' is 'CRINOID'.
Can you help me to learn more?
(Another definition for crinoid that I've seen is " Echinoderm".)