I'm collecting free iodine, uranium and another element (7)
I believe the answer is:
iridium
'element' is the definition.
(iridium is a kind of element)
'i'm collecting free iodine uranium' is the wordplay.
'collecting' is an insertion indicator.
'free' becomes 'rid' (to be free of something is to be rid of it).
'iodine' becomes 'I' (I is the chemical symbol for iodine).
'uranium' becomes 'U' (U is the chemical symbol for uranium).
'rid'+'i'+'u'='ridiu'
'im' enclosing 'ridiu' is 'IRIDIUM'.
'and another' acts as a link.
(Other definitions for iridium that I've seen before include "Heavy brittle metallic element of the platinum group" , "Hard silvery metal" , "Hard metallic element" , "Heavy corrosion-resistant metal, used in alloys" , "Hard metal element, Ir" .)