Plus ça change

The unclued Across lights (Individually or as a pair) are defined by the unclued Down lights (individually or as a pair).
 

Across

 
1    Consistent growth, as an unflappable batsman? (14, two words)
11    Dull-grey pelt (5)
12    Apparently futile flower (4)
13    Gay Tory awkwardly embracing Republican (5)
14    Poor bats frequently seen in Tom’s midnight haunt (7, hyphened)
17    Small horse alternatively antelope (5)
20    Scottish Forest Park to which work unit returns, drinking lemon squash (8)
26    Joiner points to range (5)
27    It yields oil...