Watchful dog almost yields from time to time (5-4)
I believe the answer is:
sharp-eyed
'watchful' is the definition.
(thesaurus)
'dog almost yields from time to time' is the wordplay.
'dog almost' becomes 'sharpe' (I can't explain this - if you can you should give a lot more credence to this answer).
'from time to time' indicates alternate letters (letters removed on a regular basis).
The alternating letters of 'yields' are 'yed'.
'sharpe'+'yed'='SHARP-EYED'
Can you help me to learn more?
(Another definition for sharp-eyed that I've seen is " Quick to notice".)