Electric looms weaving over time producing something desirable (10,4)
I believe the answer is:
collectors item
'something desirable' is the definition.
(rare item desired by collectors)
'electric looms weaving over time' is the wordplay.
'weaving' indicates anagramming the letters (letters weaved together differently).
'over' is an insertion indicator.
'time' becomes 't' (abbreviation).
'electric'+'looms'='electriclooms'
'electriclooms' is an anagram of 'collectorsiem'.
'collectorsiem' placed around 't' is 'COLLECTORS ITEM'.
'producing' acts as a link.
(Other definitions for collectors item that I've seen before include "rarity" , "much sought-after object" , "Object that's precious" , "something rather special" .)