Book showing a form of gneiss seen around Spain (7)
I believe the answer is:
genesis
'book' is the definition.
(I've seen this before)
'a form of gneiss seen around spain' is the wordplay.
'a form of' indicates anagramming the letters (the letters need to be in another 'form').
'seen around' means one lot of letters goes inside another.
'spain' becomes 'e' (abbreviation for Espana).
'gneiss' anagrammed gives 'gensis'.
'gensis' placed around 'e' is 'GENESIS'.
'showing' acts as a link.
(Other definitions for genesis that I've seen before include "Birth, beginnings" , "Origin or formation of something" , "name of group" , "First book of the Bible" , "Beginning the holy book" .)