Agents shield Philby, their leader revealing the most (9)

I believe the answer is:

skimpiest

'revealing the most' is the definition.
(skimpy clothing is revealing)

'agents shield philby their leader' is the wordplay.
'agents' becomes 'spies' (spy is a kind of agent).
'shield' indicates putting letters inside (some letters protect or shield others).
'philby' becomes 'kim' (spy Kim Philby).
'leader' indicates taking the first letters.
The first letter of 'their' is 't'.
'spies' going around 'kim' is 'skimpies'.
'skimpies'+'t'='SKIMPIEST'

I've seen this clue in The Independent.

Want a hint initially instead of a full solution? Install my app