All pearl clusters aligned (8)
I believe the answer is:
parallel
'aligned' is the definition.
(I've seen this before)
'all pearl clusters' is the wordplay.
'clusters' indicates an anagram (letters cluster in another way).
'all'+'pearl'='allpearl'
'allpearl' with letters rearranged gives 'PARALLEL'.
(Other definitions for parallel that I've seen before include "equivalent" , "Continuously at equal distances apart" , "Circle of constant latitude" , "(Of lines) meeting at infinity" , "Correspondence" .)