THEME:   first word of phrase is spelled backwards but the word BACK is missing   
GOOD ONES:     Deep-sea creature, literally   PMUH WHALE [humpback whale: four other theme entries are as clever]   
Rock blasters   AMPS [I thought TNT'S]   
Apple variety   IMAC   
Goal for a runner   SEAT [politico]   
Goes out for a bit?   NAPS   
Unpopular spots   ACNE   
Fire proof   ASH [two words]   
Big brass   TUBAS [not generals]      
BTW:   Blockhead   SCHMO [that's a moldy oldy]      
Michael Jackson, e.g.   ROCK 
ICON [an icon is properly a picture of an important person or thing;  MJ was an idol.  Marilyn Monroe's dress being blown from below is an icon; she was an idol]      
Odd that 
The Seven Per Cent Solution entry abuts another Sherlock Holmes entry, well, maybe not so odd as the game may be afoot.      
Really, really cool   EPIC [first and only time I heard this meaning of 
epic was in 1992 when k.d. lang said same of Roy Orbison's lyrics --- not that I remember the date; it's from 
Black and White Night CD recorded then]      
Enero, no matter the Spanish clue, is not legit.         
RATING:    
 
  
 
Three grins = Loved it; Two grins = Enjoyed it; One grin = A bit bland for my taste; One teardrop = Not much fun