Both mean "clear", but in what way these two words are different?
明 = bright = clear (you see thing clearly in bright light)
确 = definite; unambiguous = clear (when there is no ambiguity, it is clear)
明确 = clear (clear and definite/ unambiguous)
清 = clear (when water is clear, you can see things in it clearly)
楚 = neat = detailed; comprehensive (when things are neatly displayed, you can see the details)
清楚 = clear (clear and detailed/ comprehensive)
明确指引 - clear (and unambiguous) guidelines
清楚指引 - clear (and detailed) guidelines
目標明确 - the goal is clear (and unambiguous)
目標清楚 - the goal is clear (and comprehensive)
More detailed example:
清楚說説每一個細節 - Clearly explain every detail (everything you can think of and everything you can't think of is explained)
明确指出今次行動的目標 - Clearly point out the target of this mission (pointing out and confirm that guy is our target)
Simply put, just remember "明确" as unambiguously clear; "清楚" as comprehensively clear.
Of course, the English word 'clear' implies both 'unambiguous' (e.g. it is clearly him) and 'comprehensive' (e.g. everything clear?). That's why both "明确" and "清楚" can be translated as "clear"