Artist regularly cried about entering Lego building (2,5)
I believe the answer is:
el greco
'artist' is the definition.
(I've seen this before)
'regularly cried about entering lego building' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'about' becomes 'c' (abbreviation for 'circa').
'entering' is an insertion indicator.
'building' indicates anagramming the letters.
The alternating letters of 'cried' are 're'.
're'+'c'='rec'
'lego' anagrammed gives 'elgo'.
'rec' inserted within 'elgo' is 'EL GRECO'.
(Other definitions for el greco that I've seen before include "Sp. painter, born Domen- ikos Theotokopoulos" , "Crete-born Sp. painter" , "Domenikos Theotokopoulos" , "Spanish painter born 1541 in Crete" , "Spanish artist born in Crete" .)