Watch ever so unreliable, black inside (7)
I believe the answer is:
observe
'watch' is the definition.
(observing is a kind of watching)
'ever so unreliable black inside' is the wordplay.
'unreliable' indicates an anagram.
'black' becomes 'b' (as in pencil classifications).
'inside' means one lot of letters goes inside another.
'ever'+'so'='everso'
'everso' anagrammed gives 'oserve'.
'oserve' going around 'b' is 'OBSERVE'.
(Other definitions for observe that I've seen before include "Verbose (anag.)" , "Keep; notice" , "See - keep - remark - maintain - celebrate" , "See - say" , "Notice or conform to, rules say" .)