With a tern flying round above, it's decorative (6)
I believe the answer is:
ornate
'decorative' is the definition.
(I've seen this in another clue)
'with a tern flying round above' is the wordplay.
'with' means one lot of letters goes inside another.
'flying' is an anagram indicator (letters fly around into new positions).
'round' becomes 'o' (o is a circular letter).
'above' means one lot of letters go next to another (in a down clue, some letters go above others).
'tern' anagrammed gives 'rnte'.
'a' going inside 'rnte' is 'rnate'.
'rnate' put after 'o' is 'ORNATE'.
'it's' acts as a link.
(Other definitions for ornate that I've seen before include "Fancy" , "Over-decorated" , "Richly decorated, perhaps too much so" , "Excessively decorated" , "Baroque" .)