Reliable team playing for colleague (10)

I believe the answer is:

stablemate

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'for colleague' is the definition.
(stablemate can informally mean a colleague)

'reliable team playing' is the wordplay.
'reliable' becomes 'stable' (I can't justify this - if you can you should believe this answer much more).
'playing' indicates anagramming the letters.
'team' anagrammed gives 'mate'.
'stable'+'mate'='STABLEMATE'

Can you help me to learn more?

(Other definitions for stablemate that I've seen before include "someone from same place" , "One from the same organisation or background" , "companion" , "Maybe fellow Arab" , "colleague in same organization" .)

I've seen this clue in The Daily Express.

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