Fixed tie clip containing cross - that's crystal clear (8)
I believe the answer is:
explicit
'crystal clear' is the definition.
(thesaurus)
'fixed tie clip containing cross' is the wordplay.
I cannot really see how this works, but
an anagram of 'clip' is 'plic' which is located in the answer.
'cross' could be 'x' (X is cross-shaped) and 'x' is found in the answer.
an anagram of 'tie' is 'eit' which is located in the left over letters.
No letters remain.
This explanation may well be incorrect...
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for explicit that I've seen before include "leaves nothing to the imagination" , "Stating something in exact terms" , "Fully stated" , "Precise - outspoken" , "Spelt out, clear" .)