Rough guess came close and worked out at times (8)
I believe the answer is:
estimate
'rough guess' is the definition.
(I've seen this before)
'came close and worked out at times' is the wordplay.
'came close' becomes 'e' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'worked out' indicates an anagram.
'at'+'times'='attimes'
'attimes' is an anagram of 'stimate'.
'e'+'stimate'='ESTIMATE'
Can you help me to learn more?
(Other definitions for estimate that I've seen before include "Judgement of approximate value or size" , "Calculate - valuation" , "Calculate approximately" , "Tease Tim (anag.)" , "Judge the worth of" .)