It's easy to pick up what was illuminated outside Grand Hotel (5)
I believe the answer is:
light
'it's easy' is the definition.
('light' can be similar in meaning to 'easy')
'illuminated outside grand hotel' is the wordplay.
'illuminated' becomes 'lit' ('lit' can be a synonym of 'illuminated').
'outside' is an insertion indicator.
'grand' becomes 'g' ('G' can be a synonym of 'grand').
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'g'+'h'='gh'
'lit' enclosing 'gh' is 'LIGHT'.
'to pick up what was' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for light that I've seen before include "Pre-eminent person; window" , "Low in density" , "Moored vessel warning sailors of a hazard" , "Amusing" , "What smoker may be requesting" .)