Weak identity becoming clear (6)
I believe the answer is:
limpid
'clear' is the definition.
('limpid' can be similar in meaning to 'clear')
'weak identity' is the wordplay.
'weak' becomes 'limp' (I've seen this before).
'identity' becomes 'id' (I've seen this in other clues).
'limp'+'id'='LIMPID'
'becoming' acts as a link.
(Other definitions for limpid that I've seen before include "Clear and transparent, water say" , "Clear and bright" , "Calm" , "Clear (writing, water)" , "Crystal clear, transparent" .)